I also marched what we had, and stood and played the rest of the show (or what we had of it). Even if isn't 100%, the parents get a good reference point.
Water balloon toss with seniors and their parents. Pair up each senior with one parent. Start 5 yards away, after 2 tosses (to parent and then back), back up 5 yards, last senior wins!
Our boosters bring popsicles and ice cream sandwiches and soda.