Hi and welcome to the forum.

Sounds to me like you've given the family relationship building the old college try and it isn't working out. So, give it a rest for a while. Take your vacation where you want to take it and with whoever you want to take it with. Send Mom and Dad a nice, cheerful postcard to let them know you're thinking of them.

Put some distance (figuratively) between yourself and your family by declaring a year or two moratorium on visits back to the UK. You're an adult and if visits back to the old sod just make everyone (including yourself) unhappy, then dispense with them for a while. Continue to write or call if you like - or don't bother if you don't want to. After a break of a year or two, then see how you feel. You can't make other people happy if they insist on being unhappy. It sounds like you're doing just fine.
Cheers,
Bev