Probably more a WWYD than an AIBU really.
Every year since I was born I've gone on holiday to the same place in Wales. My parents used to own a caravan there so it was easy. Added to this, I'm HFA and like the familiarity. I made a friend (J) there when I was 15 and she always comes on holiday with us (me and DD) too now (so for nearly 30 years). We've camped for the past 10 ish years since the caravan was sold which I love. I love the smell of the tent, the sound of raindrops in the night, the feel of being outside. It's sensory heaven.
8 years ago I met my husband so now it's me, J, DD, and DH. ILs asked a few years ago if we'd mind them tagging along for a few days but them staying in a B&B. Fine, not a problem. Then next year it was a week, then the whole time and now there's just an assumption that it's 'the family holiday'.
Last year DS was born and ILs offered to pay the difference so we could stay in the B&B rather than camping with a newborn. It was lovely but me, J and DD really missed our tent. Also ILs said SIL wanted to come too.
This year ILs said SIL wanted to go somewhere different so I reluctantly agreed. It was nice, but it didn't feel like proper holiday to me. Now they've found a nice holiday cottage for next year which they want to book. Problem is it only sleeps 6. They want to leave J behind because 'she's not family'.
So would I be unreasonable to say no to it all, book our 2 weeks at the old campsite just like the good old days and leave the ILs and SIL to sort themselves out?
[wimp who doesn't do confrontation emoticon]