We're big fans of anything you can cook in aluminum foil - either on the grill or campfire. Super easy and NO DISHES! Heavy foil works best, but you can use whatever you have. Depending on the ages of the kids, grown ups can do the cutting and kids can assemble.
A few faves...
Sliced potatoes with peppers & onion - layer with pats of butter or EVOO, S&P and toss on the coals/grill until tender.
- also works with summer squashes, sweet potatoes, mushrooms...
You can do something similar with fruit for dessert - stone fruits and apples work great. No need to peel, just core/pit, cut into wedges and layer in foil with either sugar (white or brown) or honey, cinnamon/nutmeg to taste and a pinch of salt. If you're feeling adventurous, put a grind of black pepper on there.

Toss on the grill until the fruit is tender. Really delicious with a scoop of ice cream on top!
Banana boats (fun for kids!) - peel a small strip of the peel off on the inside curve of the banana (about 1" wide), leaving the rest of the skin intact. Put a slice in the middle of the banana's flesh, careful not to poke through the skin on the other side. Now the fun part...
Stuff it! Chocolate chips (or other flavors) or bits of candy bar, mini marshmallows, m&m's, peanut butter.... use your imagination! Wrap the entire banana in foil and put on hot coals (or the grill). Cook until the banana is soft and the stuffing is melted and delicious. Add ice cream or whip cream and eat right out of the foil with a spoon.
