His attitude and way of thinking gives me the ICK.
I know someone who goes (her, DH & 2 DC) to a top resort skiing every single Christmas. Guess what? They've never had to pay for it. She has a rich Dad.
I know another two families, again with 2/3 children, who go on lavish holidays several times per year, and again, their parents pay for them!!
In other words, looks can be deceiving.
I have family who go on about 4 holidays a year, and lavish ones at that, but they are actually very well off. I do not know anyone who goes on that many holidays per year otherwise.
Your DH doesn't live in the real world. I'd consider my DH & I to be pretty normal, we're not well off but not hand to mouth either, and we certainly do not holiday regularly at all. I'd never spend £15K on a holiday either, and we don't even live hand to mouth. It's been about 7 years since we went abroad (eurostar), our children have never been on a plane, and when we do go on holiday, we tend to stay in the UK. Our children know no different and are not missing out on anything, they love our inexpensive UK trips.
If he doesn't cancel this trip, he can go alone as far as I'd be concerned in your shoes. I certainly wouldn't be paying back HIS loan either. He can jog on. Let him sulk all he wants about HIS stupid, selfish, irresponsible decision that he couldn't even be bothered to discuss with his WIFE.
Total manchild.