I used to work in food service but 60 teens is a lot. I'd stick with finger foods, do large trays of dips, make large sheet cakes or cobblers (those large metal trays are your friend in this situation).

Sandwiches get groody/soggy pretty fast due to the mix of wet and dry ingredients so they aren't my favorite for a large party. It's just hard to find a good temp to keep them at.

Terrible idea. Just reserve a room at Maggianos and enjoy your grad's success.

Did you do this, OP? Can you give us an update?

Not OP, but I just had a self-catered grad party. About 50 kids came from the 60 invited, and I spent about $350 total on ingredients for finger foods (afternoon party with sandwiches, snacks and cookies) and decorations. The music playlist was more important than the food honestly. The biggest surprise was I was told kids won't stay long, but they did, and some stayed for 2 hours after the end time, so I guess that was a good sign. I am glad I did it but also glad it's over.