I probably am but would love a second opinion

[bumblebeet]

We are a family of four, DP has his own business but it doesn't earn us much money, I work pt 3 days a week. We have a few breaks a year, usually camping or a cheap cottage for a weekend.
My SIL and her partner do not have kids, they both work full time and earn enough to have savings and a decent pension.
In the past we have gone away for a weekend with them, a couple of times. We pay two thirds and they pay a third. Worked out per person.
They keep asking about going away as they want to spend time with the kids but it's difficult for us to afford this.
Would it be reasonable to say that we could go if they would be able to pay half.

I know that we chose to have kids and we chose for me to work pt but it is them who want to go away and who can afford to.
AIBU?

offer to let them take the kids and you and DH stay home for some 'quality time'

'We already have two camping trips and a summer holiday booked so unless we were going with them we wouldn't book another.'

Then don't. Sounds like plenty. Invite them along to one of those camping trips and they can book their own pitch.