The subs are a big hit, you could do deli trays and let them self assemble. You would want 1 heavy salad (potato and/or macaroni/pasta) and one veggie or green salad or relish tray; and I suggest fruit trays.
The baked pasta is the other great choice for this meal. See the spaghetti dinner for 50-60 at the bottom of the spaghetti page for help with the amounts, make 1 1/2 times the amounts, they are teens, after all, and tend to eat like locusts.
Check the beverage planning page for help with beverages or soda.
With teens, chips and dips are almost essential, especially with a sandwich meal. 2 ounces chips per person, 1/4 cup dip.