I feel for you @Aliceinwonder1
I'm a grandparent and we had had an opportunity last year for a 'grand' family holiday with free (distant family) accommodation. It had to be during school holidays so flights were mega expensive.
Dh and I paid for all the compliated car hire while we were away (didn't disclose to dcs how expensive that was), we subsidised some of the flight costs for the families that were struggling (not openly, but by getting block bookings and we paid for all the luggage, seat choice, plane food, fast boarding - ds paid the cost of their family flight only tickets). dh and I paid the domestic extras on the free house - laundry, cleaning etc.
Then when we were on holiday we all shared the food costs equally, whether eating in or out.
For our dcs I think it felt like an expensive holiday, but well worth it to be all together, and I think they felt they all contributed.
dh and I look at our total bills and feel pale and sweaty!!
But the reality is that our dcs could not have afforded that holiday if they had paid their exact share - the cost of hold luggage and pre-booked plane seats would have taken one family out of the equation!
It was a one off, we won't be doing it again. But as a couple, as parents, as grandparents, it was worth it.
Maybe, sometime in my dotage, they will take me out for a wee sherry and an afternoon tea!