I feel like we need way more context.
50 people and one campfire? 50 people and multiple campfires? 50 people and some grills?
Are you cooking the first day or the last?
How old are the kids?
Are you packing the food in, or driving up to the campsite?
Will you have help preparing the food? Do you want to involve the kids in preparing the food (e.g. this is a cub scout trip. 25 kids, with 25 parents who might want to work on a cooking project together).
Do you need to accommodate allergies?
Here are my thoughts for the two extremes.
1) This is a rafting trip for teenagers and adults. You have 1 campfire and you have to cook 100% by yourself. You are responsible for everyone, gluten free people, allergic people, etc . . .
Breakfast: Bagels (including some gluten free ones) and a selection of toppings (cream cheese, hummus, sunflower butter, jelly) and cut up fruit, with hot water heated over the fire, and tea bags, hot chocolate mix, and press coffee pots so people can have hot breakfasts.
Lunch: Premake two versions of pulled barbecue at home (e.g. pork and soy curls). Heat over camp fire. Serve with various raw veggies, and a choice of ranch or hummus to dip, plus potato chips.
Dinner: Set out a variety of deli meats and cheeses, and breads, and condiments like mayo. Add chips and a bunch or raw veggies and things to dip. Cook s'mores over the fire after.
Other extreme: Cub scout trip, with lots of people eager to help. Cooking over the fire is an activity. There are multiple fires and multiple grills. Magically either no one has celiac or allergies, or people with allergies will take care of themselves. On the other hand, younger kids are more likely to be picky. So do a make your own thing!
Breakfast: I'd probably still do the bagels as described above.
Lunch: Parents and kids work in team to make naan pizza and cook them on grills. Veggies and fruit. Cookies you brought from home for dessert.
Dinner: Make foil packets and bury them in the embers. Offer choices and each team makes their own. Here are some ideas:
https://www.freshoffthegrid.com/foil-packet-meals/
S'mores for dessert.