I don't know why people are saying this is normal. I don't think it's normal for a 14 year old to be out of the house 12 hours a day - what is he doing all that time and where is he? I don't think it's normal to stay up until 3am gaming - why hasn't someone sent him to bed? I don't think it's normal to sulk and moan if you are lucky enough to be taken on holiday - why is anyone putting up with this?
FWIW I have an 18 year old and she is really excited about our holiday next week. She goes to bed at a reasonably sensible time (prob midnight with no school atm), she isn't out of the house all the time (she is out quite a lot, parties and pub quizzes and at friends' houses, but also has friends over here and hangs out with her parents quite a bit). She's never once sulked or moaned about going on holiday in her entire life because she knows she is lucky that we can afford one.
Our holiday next week involves staying in a nice house in a nice place with some friends of ours and their much younger kids (who she likes and will play with). She is also getting to bring a friend for a few days. It hasn't been arranged entirely around what she would like because I'm not 18 and don't want to go clubbing. But she will still have a nice time, meals out, swimming, being in a beautiful place - and she will appreciate it.
I just don't get it or understand why anyone is putting up with such poor behaviour. I can remember not particularly wanting to go on a walking holiday in Wales when I was 14, for instance, but I also did not moan and complain about it because that's just rude.
It sounds like you have set few boundaries, OP, and are continuing to do so by planning everything around your son. You are a person too and also deserve to enjoy your time off. Maybe start planning around what would look like a good time to you and if he moans and complains, fine, off the the grandparents with no wifi it is.