I'll share with ya'll the way that I usually teach meal prep for Philmont dinners. It does involve both large cooking pots, and a normal whisperlite style stove, but to be honest, it isn't too much to expect a 12 man expedition to carry these things.
Since none of the food requires cooking, all you have to do is rehydrate it. Simply boil about 4-5 liters of water (for the entire crew) in one pot (or if you're really enterprising and have two stoves, boil 2-3 liters in two pots!).
After the water boils start out with one of the pots completely empty, and add a few cups full of water to it. Then start dumping all the food packets in (mashed potatoes, chicken pot pie, etc.). The things that don't make sense to mix (i.e. green beens and mac and cheese) don't mix, but the majority of meal items go very nicely together in a 1 pot method.
Meanwhile, have the cook add a cup of water to the pot with the food in it, until it looks to be about the right consistency. Keep stirring, and cover and let sit. A few minutes later your meal should be ready to eat.
The beauty of this is it eliminates the clean up mess that comes from trying to cook dehydrated food over a stove. You just end up with burned stuff on your pot. Once you eat all the food, cleaning the "cook" pot requires no more than a few wipes with a sponge and you're done. You can even use the leftover hydrating water (which should still be warm) as your cleaning water.
I noticed someone mentioned the individual tupperware method. From what I could tell that method also works really well. Just make sure if you're planning to use that method to incorporate it in all of your training hikes so the boys all know how to do it properly.
What I would not recommend are turkey bags or especially trying to rehydrate the food in the foil packages. It's usually just a disaster waiting to happen. Especially the foil package method. The bags are too small to add water to with all the food inside, and it'll just spill everywhere. Turkey bags really aren't worth the effort in cleanup that they save either.
I hope that helps some. Also, a note on the food bulk. Yes it is a lot of food, and yes it does take up a good bit of space, but it all usually tends to get eaten :)
Good luck on your treks.