Plan your own vacations when you want to, and plan a suitable combined vacation with this other family when you want to. If they freak out at your planning your own vacations as you see fit, then let them. Bowing to unreasonable demands because someone will make you pay emotionally if you don't is not a healthy option.
Carolyn HaxIf you're not sure what you want, then hold back from making plans or responding to invitations until you have a chance to think about it.
Carolyn HaxThere has been, for some reason (or more likely an unfortunate accumulation of reasons) a trend over the past several decades for parents to do the work of parenting in the isolation of their own homes - and not only that, this trend has overlapped with the other trend of much deeper parent involvement in raising kids. That you also represent trend No. 3, more people raising kids solo, has only exacerbated a close-to-no-win situation.
Carolyn Hax