"Mindless" is probably the limiting factor for this problem. How a mindless servant reacts to this kind of command is simple, really. Imagine how another mindless creature, such as a servant zombie, would react.
Unfortunately, I do not see a servant zombie walking ahead, peeking around the corner, and then calling out "I see three orcs and a goblin, my master!" It is unable to communicate the results back to you!
You might be able to get it to communicate some simple results. The command "If a creature is around the corner pick up that pebble and hand it to me" would likely be successful, but if he handed you the pebble you have no way of knowing if the 'creature' was a rat or an ogre.
The Spell Animate Objects effectively turns 'objects' into 'creatures.'
Each target animates and becomes a creature under your control until the spell ends or until reduced to 0 hitpoints.
Creatures occupy space on a battlemap, they don't just hover in an enemy's space. In fact, they can't.
Whether a creature is a friend or an enemy, you can’t willingly end your move in its space.
As these creatures are Tiny, per PHB 191, they take up a 2.5 ft x 2.5 ft space...meaning you can fit four of them into a standard 5 foot battlemap hex.
So, in dealing with this spell, you would track the location of each 'creature' created by Animate Objects separately on the battlemap, where they have a Fly speed of 30' for the purposes of moving around. If you want to make your life easier, clump them into groups of 4, and track them that way.
In essence, Animate Objects works just like a conjuration spell where you summon up a pack of wolves. They have a space they occupy just like every other creature on the map. And you determine if they were hit by a spell the same way. Technically, they should even roll their own initiative, as the spell specifies:
You decide what action the creature will take and where it will move during its next turn
Emphasis Mine (For simplicity, I personally just have them all act on the caster's turn)
As for how many attack each round? As many as all of them, assuming they are in range of a creature they can hit.
As a bonus action, you can mentally command any creature you made with this spell if the creature is within 500 feet of you (if you control multiple creatures, you can command any or all of them at the same time, issuing the same command to each one).
Best Answer
This could work but it's probably up to DM fiat
Spellwise I'd agree with your interpretation, it could be possible to make this work, provided that the tiny servant is created, dispatched and capable of returning within an eight hour period. The command could also arguably be expressed pretty simply - 'As soon as a message has been securely attached to you, return to me, in my tower'.
However, there are a number of things you might want to think about, about which there's no real RAW guidance:
These could all be fun questions to consider as part of your narrative. Has the wizard had a limited success rate doing this in the past? Unbeknownst to the wizard, is the town on high alert, searching for the mysterious 'cutlery killer', recently implicated in a number of deaths?
Note: Thanks for the interesting idea hohenheim. I'm very tempted to incorporate something like the following into my own campaign: