I would suggest you back into the level based on the amount of time you're willing to commit to character creation. In my experience, there tends to be a non-linear relationship between character level and time required to create the character from scratch. Let's create a simple model of how long it takes to make a character (assuming players are familiar with the process):

• 15 minutes base for a concept, name, abilities etc.
• 10 minutes per level for powers, hitpoints and other level-dependent choices
• 10 minutes per tier above heroic, representing the additional complexity

This gives us twenty-five minutes for a first-level character, and about two and half hours for a eleventh-level character. Your model may be different, and will likely have different values based on your group. Use your model to calculate how many levels of a character your group can build based on the time you've allotted for prep.

For example (using my model): You have a short game running about four hours, and you can only allot 45 minutes to character generation: you would calculate that your players can build level three characters in that time, so build a level three adventure.

There is no direct porting guide whatsoever and directly porting characters to emulate their tactical abilities in 4e is probably impossible.

5e's combat and class system is wildly different from 4e's. Combat rules are much lighter (charging is only possible if you spend a feat and even then its very sub-optimal, for example) and overall emphasis of combat spells and abilities are to 1. do more damage 2. make more attacks (also so #1). and 3. force a save roll vs. an effect.

Within the bounded accuracy of 5e's system save attacks are somewhat iffy, especially against large groups, PCs to not have access to sure-fire effects on hit or effects that last "until the end of your next turn" as they did in 4e. Likewise many of the classes are based on the versions from 2nd or 3.5 and eschew many of the features and powers that defined those classes in 4e.

With those cavets in mind here are my suggestions for those two asterix'd PCs.

The Warden may want to go Ranger or Druid and focus on spellcasting over other options Both the Warden and Ranger spell lists have some very controller-ly/defender-y spells but as with just about any spell that applies an effect they are Save DC spells based on your casting attribute which for both classes would be WIS.

The dwarf tactical warlord should be a Fighter(battlemaster) or a Bard

Battlemaster manuevers have a lot of similarities with the powers available to 4e Warlords. Notably Commander's Strike using your action to have another player make an attack with a damage buff.

If Bard, you have the eventual goal of the College of Valor class path. They might want to start level 1 as a fighter, paladin, or cleric to pick up armor and weapon proficiencies to make them more in line with the original vision of the character in 4e. Keep in mind that many of the features or powers that defined 4e classes can only be approximated through the spells PCs gain in 5e. The Bard's spell list has the most buffs that can be applied to any player.

Finally, Feats are your friend.

Feats have a steep cost in 5e, you're taking a specialty set of features vs. getting a +2 1 ability score or +1 to 2 ability scores, essentially trading +1 damage, to hit, and/or spell save DC (not to mention skill checks). That said, some of them are very much worth this trade-off. Sentinel for example gives a PC 4e-defender-style opportunity attacks and would be a perfect fit for your Warden.

You may want to consider houseruling everyone a free feat to help emphasize their previous specializations from 4e without making them wait and face the touch choice between the feat and the stat increase at level 4.