Lots of backstory so I am not drip-feeding but in summary;
My eldest DS is 11 and I have been on 4 holidays /short breaks with my DM and the children.
Also over the past 11 years, just myself and DM have been on 2 trips to US and about 4 trips to European cities Paris etc. I pay for all these, no issue with that, I have the cash. However time is challenging, I work and travel quite regularly.
The last joint holiday with DM and the children was a disaster. DM likes to stay up late drinking, I do not. DC demanded my attention, DM wants my attention, you get the drift.....
Over the last 5 years, twice we have shared 1 week of our family holiday with DS and her children (great, we all got on wonderfully)
Last year we shared 1 week of our holiday with other DB and his family (again great we all got on wonderfully) Another year we shared 1 week of our holiday with DH sisters.
Every year a 4-5 day long weekend is spent with his family. We see a lot more of my family than his, due to location.
This year DB is doing a wider family holiday with his in laws and our parents. I don't want to go as I just think its too many people and it wont be relaxing.
I know it would mean a huge amount to my DM, I know the kids would love it but my DH would hate it so AIBU to not go.