I am cooking dinner for 75 high school football players - after practice, and on a night before a game. I am servicing lasagna and flank steak torpedo sandwiches. I'm thinking fruit salad for e side and ice cream sandwiches for dessert.

Do I have enough items? Do I need meatball subs too or potato salad? Or corn on the cob?

For quantity, I'm figuring 5 pans 11x17 of lasagna, 200 torpedo rolls, 50 lbs flank steak, fruit bowl of watermelon, grapes and pineapple, and 300 ice cream sandwiches.

Is that enough? And do you have a suggestion for what to marinate the flank steak in?

Assume that they will eat like 100 adults, allowing for teen appetites and a few coaches

lasagna, 5 pans 11x17 of lasagna, OK. Consider making 1 meatless as you may actually have a vegetarian or 2 in the group

flank steak torpedo sandwiches, 200 torpedo rolls, 50 lbs flank steak,
I would plan for 1 sandwich and one extra roll each, 150 -180 rolls, but only 30 pounds flank steak; you could also do fajita style adding and equal amount of onions and peppers, and 25 pounds would be plenty. Top sirloin is another option, depending on prices. Any Italian dressing is great as a marinade- slice, put in ziplocks with the marinade overnight.
Have sandwich fixings available, see the sandwich page- sub BBQ sauce for ketchup.

fruit salad, see the fruit tray page. Trays are prettier, hold better and the leftovers are more usable.
Yes definitely add potato salad- 4 gallons, or 40 pounds raw potatoes
and baked beans or another bean dish, how about my "plain old chili beans", or my borracho drunken beans? 8-10 pounds dry, or 3 1/2 gallons canned
You could also add cole slaw, 2 1/2 gallons

ice cream sandwiches- 2 per person is very adequate and 3 is extravagant- 4 is too much