Adapted from a recent online discussion.
I have three sets of parents, two mine and one my husband's. Only my husband's family has money, and this is a source of tension with my family; to them, it seems that my affections for my in-laws were bought and paid for.
My mother-in-law really wants to take us to Europe, not once, but twice this year. I feel like I keep telling her "no," because of work or because it's the other family's turn for Christmas or whatever, but this year there is no convenient way to get her to scale down.
How in the world can I strike a balance between all of my families when one set seems to hold all the cards?
-- Balancing Families
The way you frame this, there's no "you" anywhere. The entities making all the decisions are the parents, your workplace and holidays.
What do YOU want? If you want to go to Europe twice, then go to Europe twice, and find some way to show your love for your other parents. If you'd rather not go twice, then say no to one or both trips. "I am so grateful for the opportunity, but going (twice) would mean I don't see my parents at all this year, and I want to see them." Or whatever.
And I haven't even gotten to your "I keep telling her 'no,'" vs. "we keep telling her no." Both you and your husband seem curiously absent from the meeting to plan your own lives.
Figure this out, together, and then present a kind, decisive and united front on how you want to use your vacation and family time. Money is a trump card only if you let it be.