1. Did they actually use the words, "Take them to contest"? Then do just that. Take them to contest. Sit them in the stands. Buy them a hotdog. Heck, I'd even bring them back.
2. Don't waste time on a show. March - heck walk - out on the field. Wander around (or stand there) for four minutes playing concert F's. Maybe even the fight song. Buy them a hotdog. Bring them home. Don't even wait or ask for the result.
3. Do the kids like you? Get one trustworthy kid to get them to just not show up the day of contest. Later that week buy them a hotdog.
Seriously - point out to the administration that they are putting the kids into a crushing situation. If they want to punish you, go for it, but don't let them do it by humiliating the kids that are there.