Since they will be learning most of this after they crossover, you probably want to focus on "just add water". An easy and extendable base is instant rice and ramen noodles. Adding a boullion cube and dried veggies, pepperoni,... almost anything will make a meal. The kids will experiment more than the adults. Demo a few recipes using each base and provide a "chart" with potential add-on options.

Basic recipe Examples

Pizza Rice

instant rice
spagetti sauce powder
sun dried tomatoes
pepperoni
mozzarella stick

add boiling water to first 3 ingredients, stir, cover and let rest until done. Stir again add 'roni and cheese.

Cajun Ramen Chicken

ramen noodles sans salt packet
Knorr alfredo seasoning
powdered milk (somewhat optional)
cajun seasoning
packet or can of chicken

Add boiling water to noodles, cover and rest. There should be some water not absorbed...add more if needed. Stir in next 3 ingredients, let sit until absorbed, add chicken.

The above recipes were adapted (read: simplified) from my own recipes to be age appropriate for your boys.