I'm helping to plan my sisters wedding. There's a predicament. The invite list is about 70 people long and it's technically a "destination wedding" because it's in the town she just moved to (a 17 hour drive or 6 hour flight from everyone on the guest list). Because of this, the expectation is for the list to half. If it's under 40-45 people, she'll be doing a backyard wedding. If it's over 45-50 than she has to book a venue.
What is the best way to get a better idea of how many people are coming? Can a tentative RSVP be sent out? Or maybe we can just weed out the people who are definitely NOT coming by sending a "if it's definitely a no, we'd love to know" card?
I know this is in the etiquette section, but to be honest, she's totally fine with not being completely normal or formal with the invitations. The whole family is very open and honest with each other and not afraid to say no!