Parents need to be parents. If you don't want your kid to go, tell them they can't go. That's all there is too it. However, the kind of kids who would be going to see this show are cetainly the older crowd(not 13-14 year old kids) and aren't really that impressionable. I hate that whole idea that kids are impressionable. When you're 16, you do what you do because you want to, not because someone else is doing it. It's not like your 11 years old again.
I'm sorry, I'm really not trying to be facetious or sound like a smart alec, but 16 years do a lot of things because other people are doing it. Up until you're about 25, your cerebral cortex (the part of your brain that helps you make decisions) isn't even fully developed. I happen to think 16 year olds can be EXTREMELY impressionable, why else would kids start doing drugs or drinking when they're around that age?
But hey, maybe you did do things because YOU wanted to so good for you! I can't say this is the case for every single teenager out there, but I'm willing to let it be known that I am influenced by what people do around me and I'm okay with it.