I think for the three you mentioned (AK47 AR15, and MP5) the more basic setups would be the best for novice shooters. Keep the weapons simple and basically "stock." Lose the foregrips, folding/adjustable stocks, optics, lasers, etc.
This would also give the new shooters a chance to see the guns in there original form, and aid in teaching them about the differences and similarities.
Also, the less on the firearm, the less things there are to fiddle with and overwhelm a new shooter.
In my opinion, this is a great time for the "Keep It Simple" mantra
NRA Life Member, SAF contributor.