I don't work in the school hols and I have an only DS, aged 10. She's very sociable and I enjoy having her friends around and taking them places (beach, local beauty spots for picnics) etc. I don't expect reciprocation and other parents do me favours in school time anyway, so it's not a chore.
I'm constantly being told I "do too much" but I think it's perfectly normal to entertain other people's kids, especially as we live in an area where kids don't play out.
AIBU to ask how much you do?