First off, all of edgerunner's answers are great. But I wanted to add some Dungeon World specifics:
Check p.19 and you'll see that 6- isn't "failure" - it's "trouble". The GM will say what happens and the player will mark XP. You are attaching non-DW simulationist ideas to DW mechanics by your supposition that 6- means "failure."
These principles can apply in all sorts of games, and have been used by GMs for years. If the PCs have to climb a fence, they're just going to keep trying until they succeed, right? So even in traditional games, many GMs will read "failed" rolls as a lack of some quality - not fast enough, not quietly enough, not without hurting themselves, etc., instead of just keeping them on the wrong side of the fence.
This is because failure is boring and stops moving the story forward. So you are correct, there is no plain-old failure in DW. It's not in the GM's agenda to make the PCs fail. There is no move for failure.
So the problem isn't that edgerunner's ideas are non-optimal, it's that your concept of what 6- means is wrong and that static failure doesn't exist in Dungeon World.
Expanding on 6-
From the text:
Generally when the players are just looking at you to find out what happens you make a soft move, otherwise you make a hard move.
Somewhere in Apocalypse World itself it says about hard moves:
make as hard and direct a move as you like
Early PbtA games like DW assumed you understood Apocalypse World. And this phrase is often tacitly implied in PbtA games even today.
6- means trouble as I said. The GM is free, on 6-, to make a move as hard as they like. That doesn't mean as hard as you can think of.
AW says:
It’s not the meaner the better, although mean is often good. Best is: make it irrevocable.
So while a 7-9 should substantially give the character what they wanted (they accomplish their intent even if their action created complication), on 6- you are free to deny the intent (the action still has to have consequences beyond "no" though) and in addition make a move as hard and direct and irrevocable as you like.
Climbing a mountain a soft move is "The boulders above you on the rock face begin to wobble as the grappling hook you've tossed up there sets itself. What do you do?"
A harder move is "The boulders have tumbled off the edge of the ledge and after hanging nearly motionless for a tiny instant above you, are now plummeting towards you, gaining speed every moment. What do you do?"
A really hard move is "The boulders are yanked free by your grappling hook and come smashing into you, tearing you from your narrow perch and scattering the contents of your pack into the yawning emptiness beneath. What do you do?"
I have experience bringing kids (my own son and his friends) into RPGs. I have experience with Dungeon World. I have experience with Fate and FAE. However - I do not have experience introducing kids to RPGs with Dungeon World or FAE. Just to be explicitly clear.
With that being said, as the probable instigator of this question, I feel that it is incumbent upon me to at least attempt an answer, so here goes:
Both games are products of a new school of game design. They fall into a category I will call here Fiction First. In neither game is the answer to the question What do you do? present on the character sheet. Ever.
In a Fiction First game, the game is played by talking - it is a conversation, where the GM describes situations and then poses the essential question of roleplaying, What do you do? Players answer and the GM rolls the outcome of their answers back into the fiction and the cycle continues, permutes, and repeats.
Dungeon World
Dungeon World is a very focused game, and it is focused upon the very genre you want to play. It is an excellent game in general, and has been an excellent vehicle for me to introduce new players - character creation is fun and collaborative and results in parties that are connected before the start of the adventure. When I warned before of the different principles, here is what I was warning you about:
Dungeon World is derived from the groundbreaking game Apocalypse World by D. Vincent Baker. One part of the brilliance of AW that shines through in DW is the concept of Moves. Moves encapsulate the mechanics of Dungeon World. You've seen them. Player moves read like this:
When you attack an enemy in melee, roll+Str. ✴On a 10+, you deal your damage to the enemy and avoid their attack. At your option, you may choose to do +1d6 damage but expose yourself to the enemy’s attack. ✴On a 7–9, you deal your damage to the enemy and the enemy makes an attack against you.
That's Hack and Slash, a basic player move, from the DW SRD.
The structure of a move is very important - it defines an inflection point in the fiction - a point at which the mechanics kick in - and describes simply but exactly what to do and how to fold the result back into the fiction. A move is invoked by an action in the fiction that triggers it. But a player may never state, "I Hack and Slash the ogre!" - The player has to describe something that triggers the move instead. This is what I mean about the answer not being on the character sheet. This is confusing to some people, especially those used to selecting options from video game menus or boardgame actions.
But Dungeon World is an asymmetrical game. You, the GM, are not playing the same game as the players are. The GM has moves, yes, but they are not the same as player moves. They do not have a trigger/roll/consequence structure. You, as the GM, will probably never roll dice. I usually have my players roll damage for my monsters and other threats. Your moves are things that just happen in the fiction. You say it, it happens. From the gazeteer:
Whenever everyone looks to you to see what happens choose one of these. Each move is something that occurs in the fiction of the game—they aren't code words or special terms. "Use up their resources" literally means to expend the resources of the characters, for example.
- Use a monster, danger, or location move
- Reveal an unwelcome truth
- Show signs of an approaching threat
- Deal damage
- Use up their resources
- Turn their move back on them
- Separate them
- Give an opportunity that fits a class’ abilities
- Show a downside to their class, race, or equipment
- Offer an opportunity, with or without cost
- Put someone in a spot
- Tell them the requirements or consequences and ask
So - players take fictional actions and trigger moves. You use your moves to create fictional actions and / or situations. If a monster has a move like Call for reinforcements, that's exactly what it is - but there will be no check, no percentage chance that reinforcements hear them - what happens is what makes sense in the story. Are all the other goblins (or whatever) dead? Did they already call for reinforcements? Did the players already eliminate or make a deal with those reinforcements? Are they too far from the lair to hear? That's all up to you and what makes sense given the story so far.
You don't really need much in the way of a planned adventure for Dungeon World, I have found. A juicy starting situation and a little local information, plus whatever you think would be super fun to throw at the players is usually plenty. The events tend to spin off on their own as players act and the rules are engaged.
FAE
Fate Core (and FAE, by extension) is a generic game - not generic in the bad sense of "low quality" or "one-size-fits none". Rather, FAE is generic in that it is designed to create adventurous stories through play, while the genre forms, tropes, settings, and specifics of those stories are outside the scope of the system.
The heart of Fate is Characters - though many mistake the (once-novel, now at least 8 years old) concept of Aspects for the game's core. Aspects are great, and they were once novel, and they changed the way I play everything. But you'll understand it better if you think of it as Characters - thus, the Fate Fractal. From the SRD:
In Fate, you can treat anything in the game world like it’s a character. Anything can have aspects, skills, stunts, stress tracks, and consequences if you need it to.
Aspects are just one piece of Characters, and a very flexible piece, but don't forget you have the whole palette of tools to choose from and get stuck using just aspects.
The brilliance of Fate Core (and therefore FAE, I'm going to stop mentioning it now) is the distillation of everything in the game down into just four actions:
- Attack
- Defend
- Overcome
- Create an Advantage
While Dungeon World provides specific moves that guide play out of the fiction, into the mechanics, and back, Fate sets general guidelines that do the same things. So one set of mechanics governs every interaction between the mechanics and the fiction, dispelling the need for the profusion of systems and subsystems that practically defined early RPGs.
So if your player says, "I want to take careful aim with my crossbow so I can be sure to hit the bad guy and not the hostage!" you take that as Creating an Advantage instead of consulting the book to find out if aiming is a free action, whether the player meets the minimum dexterity requirement, what the aim bonus for their particular crossbow is, etc. If they succeed in creating the advantage, you create the aspect You're in my sights! and proceed with play.
If you need something more complicated - the canonical example is On fire! - you can give it skills, like Burn for example, to take actions (like attacking or moving) with, and a stress track to show how far it is from being put out.
Fate isn't completely agnostic about what kind of stories it is designed to tell. What Fate seeks to model is adventure fiction - fun, exciting stories about interesting people doing risky things. And it does a great job of it.
Conclusion
- Neither game is hard to run or play.
- Neither is particularly expensive
- Both games are more similar to each other than to AD&D
- Both are wonderful games and I would not hesitate to use either one in the situation you describe
- If forced to choose, I would say Dungeon World - because in your instance, you have only a short time to play. If you had all summer, you might find that the broader scope of Fate allowed you to explore more genres.
Best Answer
The hemming and hawing should not happen, you're right.
The problem here isn't on the player side. The GM is cheating. Accidentally, but still cheating.
GM Cheating in Dungeon World
The GM cheats in Dungeon World when they speak without following their Agenda, Principles, and Moves.
There is no GM move called "make an arbitrary decision." There's also no GM move called "have a freeform social interaction." If the GM is following the rules, this kind of stall should not happen.
This is why the GM has rules, to prevent situations like this one, among other situations that qualify as failure modes to avoid.
Responding to a polite request, as the GM
The player's job is done: they've had their PC ask politely. There is no error on the player side of the equation and nothing to fix, no other moves to try to bend to fit the goal.
Since the “everyone looks to you to find out what happens” trigger matches, it's now the GM’s turn to make an appropriate move, instead of falling into “time for unstructured social exchange improvisation!” habits that they have brought with them from some other game.
(Recall too that moves aren't optional when triggered: when that trigger happens, a move must be made; this is equally true for GM moves as for player moves. The GM's turns has been triggered and making a GM move is now demanded by the rules.)
There are several moves that the GM could make. All of them, if executed with the Agenda and Principles in mind, should immediately add something new and interesting for the players to engage with, not just chit-chat.
The trick is to pick one, and then do a quick mental Mad Libs to fill in the blanks that the move demands. Let's assume the PC has politely asked for that magic sword:
Reveal an unwelcome truth:
Show signs of an approaching threat:
or
Turn their move back on them
Possibly the simplest and most straightforward move to make: ask them to tell you why in the world their polite request makes any sense! If they're asking in the first place, they might see a good reason that you're not seeing.
Give an opportunity that fits a class’ abilities
Have you got a thief in the party? Well...
Tell them the requirements or consequences and ask
This is a staple of responses to polite requests. This prompts the GM to set a price, and ask.
or
or
or
The point is that the PC “just” asking is just the beginning, and there is nothing that says “just asking” is suddenly set in stone as the price at stake. The GM's job is to play to find out what happens, and to do that you pick a GM move, fill out its details, and play out that response. The result will almost certainly establish that there is a price beyond politely asking, either of in-game goods to exchange or in narrative branches the players must tackle. Rather than deciding, you add something interesting to the situation and then see what the players do.
So clean up the GM's side of these meandering social improv interludes, and you won't see stalls anymore! The GM might even be surprised by the things they spontaneously add to the game, faced with such circumstances. This is where Dungeon World shines: turning mundane, boring bits of play into pivotal moments, because the rules demand never doing something boring and stale.