Christening party delimma AIBU

[JoJoIrishgal]

So having a christening for baby. DP and MIL have turned it into a full blown party for them and their friends. I feel genuinely not listened to. We financially can't afford a big party. Each time they bring up who else they have invited it fills me we pure genuine dread.
My idea was close family, god parents and a few friends, 30 ppl max.
Am I being unreasonable?

so they just expect me to take the kids home while they party

What ??!!
I would make it clear that if some people want to have a party, then of course that's fine - but they arrange their own.

IME a 'Christening Party' is people having lunch after the service (if part of the morning service) or a buffet tea if it is in the afternoon.

I do think that you and your dp need to agree what 'event' this is, who is doing the work, who is financing it, and for him to tell his Mother that she had the chance to arrange his christening. This is your and his baby, not hers.