How to figure portions for kids

I think you should allow good servings each child, per the foods mentioned, and a back up of at least 15 , more for safety, and most kids will want ..subs ,tacos nachos in that order 4 oz of a meat type product , and a snack type about 3 oz, and if a 6 inch sub, that is a standred meal by itself, so id say 150 subs, 50 tacos 100 nachos, and 5 extra of each, of the 3 , type meals ive helped with this type project before and that what i think , but have backups for the kids so they get all they want also

We are doing a snack tent for kids with cancer. This will be chips, drinks, subs and tacos. What we need help with is how much ham and turkey to buy, how many sub buns, bags of chips and so on. We were told to plan on 200 people.