I am going to the festival and that is final and is not not up to debate. You guys have your opinion and i have mine.....NOTHING is certain here in life anyways, so taking a (small) risk on my ears/T is just many of lifes everyday risks.
My only advice is this: do not let anxiety take hold after the festival. Do not worry whether your tinnitus is louder. I'm not saying it will be, but I think that anxiety can take over -- and anxiety can make tinnitus worse.
I spent yesterday at quite a few fun places with my kids. Doors slammed, babies cried, vehicles drove by, a loud bell clanged, etc.
My tinnitus was screeching in both ears by the evening. Anxiety began to creep in while I worried if I'd overdone it and worried about all the things I fear I won't be able to do anymore. But then I calmed down and considered some other key factors: I had not drank or ate enough, I was hot and slightly sunburnt, I had been on my feet all day, I was exhausted, and I had an absolutely horrible headache. All things that on their own increase my tinnitus.
So I drank a few glasses of water, went to bed early, and ignored my worries. It was back to it's usual level by morning.
I guess I lied, I have more advice: use sunscreen, drink enough water, wear comfy shoes, get enough sleep, and don't hesitate to leave early if you or your ears are tired.