Why is going at a Carol concert a problem? I am not long back from abroad where (as a Christian) I was absolutely delighted to join in the local Diwali celebrations, joined in with a family for a ceremony honouring Ganesha (the Elephant-headed God) as a precursor to a family wedding, followed by Garba dancing and then at the Hindu wedding ceremony itself and the reception afterwards. I happily join in with New Year celebrations, be they Gregorian, Christian, Hindu, Jewish etc.
I do admit I have a bit of a problem with ritual sacrifice and mutilation, but that is about as far as it goes.
As for being offfered alcohol - well, you don't have to accept it.
To quote Dave Berry: In the old days, it was not called the Holiday Season; the Christians called it 'Christmas' and went to church; the Jews called it 'Hanukkah' and went to synagogue; the atheists went to parties and drank. People passing each other on the street would say 'Merry Christmas!' or 'Happy Hanukkah!' or (to the atheists) 'Look out for the wall!'