Hey, that sounds like fun!! How long do you usually go without a leak? Once I got my system down, I stopped having leaks, but I did have some in the beginning. I hope you decide to go.
Just a thought, my stoma is usually active only after I eat, so maybe you can eat early in the day, so you don't have to eat much while you're at the concert.
No food = little output = less chance of leaks.