no idea why we needed a place that sleeps 10 when only 5 were originally going.
You really have no idea?!
well, I think now you know why the organiser booked a place that sleeps 10, @Jbrown76
This was clearly planned all along,
The OP wanted their children there from the start, and found a place that would easily accommodate or absorb them.
Then the “surprise reveal” that they’re coming, because I bet they didn’t want to impose the costs on their children.
So instead, they got you all to share in the initial costs agreement instead.
Otherwise if they didn’t do this (and the adult children coming are students or low wage) they’d be personally paying £255 to everyone else’s £85.
Which is fair!! I’d happily pay such a small amount to bring my kids along.
I can just see however how in their mind, they would have worked themselves into a froth about that.
As a previous poster said, she goes on holiday with others and their grown up kids, and the group agrees that the young adults are low wage etc so folk are happy to pool money to have them there etc.
Thats the conversation the booker should have had with you all, instead of silently imposing their DCs costs on you.