If you really want to see that musical, then I recommend you go, otherwise you'll regret it very much that a stupid thing like worrying about having a panic attack has held you back.
Not to say that it's stupid to worry about it, but if you let that stand in your way you're slowly cutting yourself off of everything you enjoy. The cause of a panic attack usually starts with worrying about having one and it will become a vicious circle very quickly.
If I'm about to have a panic attack (which is usually at night) I feel it well up inside me, fear about not being able to breath quickly rises up to the point that I have to turn on the light as quickly as possible to find any relief. What I found however is that I can put my mind off of it by using something that makes you feel safe. It might sound ridiculous but I have a small bunny figurine that I've always had on my night stand since I was little, it's one of those glow in the dark ones so I focus my thoughts on it and it sometimes helps to prevent my attack.
It might help if you take something that means much to you and that you had for a very long time, just believing that it'll help against having a panic attack helps greatly.
Hope this is useful to you or anyone else

.