My brother invite me to his 60 th birthday bash ( he lives in a different European country)) Luckily I'd thought about it and neither me or my dh wanted to go but felt we'd have to.when he asked I said We appreciated the invite but wouldn't be coming,it wasn't for us.
He was a bit taken aback and miffed but accepted it. I phoned on his birthday and hoped he had a lovely time.Tbh he showed me photos and it looked as I thought, not our sort of do.
Plus, it earnedme LOADS if brownie points with dh for refusing the invite!
I got sick of doing things I knew I wouldn't enjoy. No need to be unkind, just say it's not your thing. Good luck!