In browsing here, I'm reminded of a meal that my older sisters made in 4-H many, many, moons ago. Hamburger patty, sliced or diced potato and carrot, some chopped onion if desired. Other veggies...
another thing that helps is to have the veggies sliced the same thickness. When our Cub Scouts do them, I slice all the potatoes and carrots with my salad shooter. can slice a 5lb bag of potatoes in less than 3 minutes. hint... wash your potato slices with some salt water, so they don't turn brown while waiting to put in the pack. Kids will not eat Brown Potato Slices.
If you go to the reynolds foil website, they have a bajillion foil pack combinations.