70 kids if grade school, figure as 50 adult servings, and don't forget to add in the adult staff and the cooks. The quantities below are for grade school kids. Up it 10% if it is all boys.

If teens, count as adults and again, add in staff.

LUNCH..
soup, not a favorite; If you do do it, chicken noodle or chicken and stars, 3 1/2 gallons for grade school or teens. With the weather warming
suggest mini muffins, or some good rolls or bread, 1 pound per 10-12
home made chicken nuggets, 5 small, need dipping sauce. cup per 5
Vegetarian "chicken nuggets" are available, suggest at least 6 servings
peas, definitely not a kid favored veg. Green beans, broccoli, corn, all better choices. 12 pounds ready to cook or 2 #10 cans
chips 1 ounce per kid, consider the individual bags
salad, again, not a kid favorite, suggest baby carrots, 1 ounce per kid
DINNER..
meatballs in sauce, 12 pounds small meatballs, 3-4 quarts sauce

mashed potatoes,
pasta,
Why both? If you are doing meatballs, just pasta? Much less waste.
Consider looking at the spaghetti page and using the spaghetti dinner for 50-60 as a quantity guide, it will do fine fro 70 grade school age kids

salad, skip. Cut up fruit or fruit salad, see the fruit tray page for amounts
Expect dessert demand. at least pudding or ice cream

Day 2..LUNCH...
Soup,

B,B,Qued minced meat patties & sausages,

Suggest you do a sloppy joe type sauce and slider buns, 2 per grade school, 3 for high school; 1 pound ready to serve makes 5 classic buns or 12 sllders

potato wedges or steak fries, even done in the oven, would be more popular than roast potatoes, same cost. about 15-18 pounds of potatoes

salad, do 1/2 the amount for 100 on the plan for 100 page, or consider doing raw veg trays, see the veggie tray page. How about a jello and fruit salad?

Day 3 LUNCH, sandwiches, ham or chicken and lettuce, packed to go .

Again, depends on age of kids. If doing sack lunches, suggest you add 1 sandwich, cookie, carrots or apple slices or small tangerines, maybe a 1 ounce bag of chips. Plus a juice box.

There is a whole section on sandwiches. basically 1 pound loaf makes about 8 1 pound lunch meat, thin-sliced, makes 7-8. about 3 to 2 chicken is common.

Hydration is a big issue, have juice/lemonade and water at every meal.

If you want to discuss further, just write back.