Just the first things that come to mind:
Apples with cinnamon & sprinkled with nuts (a dab of butter is good too)
Bananas slightly roasted/grilled in the skin, can cut in half lengthwise or put a slit in the skin & stuff some dark chocolate chips in there. Ends up being gooey, but yummy!
Just about anything you would roast in the oven is good packed in foil with some oil/butter and seasonings and cooked above the fire. If you put directly on the fire, make sure to turn it frequently & keep an eye so it doesn't burn. Some ideas for that:
Potatoes or sweet potatoes diced up with onions, mixed with butter or olive oil and salt, pepper, garlic
Veggies done the same way (I've done this with zucchini, mushrooms, broccoli, etc)
Salmon, chicken, or other fish (add extra spices to liven these up), assuming you will have a cooler. If not, you can make one-pot meals with chicken or salmon pouches, some cut up veggies, and a simple sauce/seasonings. Sometimes I take Frontera Foods enchilada sauce as the ingredients are pretty decent.. and it is delicious with chicken & a ton of veggies (and shredded cheese, yum).
I'm sure others will have good suggestions too. Have a great trip!