@Zumbador@actuallyautistic Those three rules are eerily familiar. Not surprisingly so is the impossibility of making group decisions.
In that part of the family, if I have the energy I try to qualify my lack of preference with a reason: X might be fun, but relative Y has to get up early tomorrow morning; Z sounds interesting, but relative A isn't a big fan of crowds. At times, it starts actual conversations where relative Y is honest about their scheduling needs and relative A can express an honest opinion about whether it's a good time for being in a crowd. It fails sometimes, too, and people get defensive.
I just remembered doing this in an organization meeting once and it basically caused the person who really wanted X to get indignant and become demanding, so there's that, too.