My Mom and I are throwing a 70th birthday party for my Dad. We expect to invite 40-45 people, most are close family (sibs, neices, etc) and some are golf buddies. It's a full sit-down dinner. I think that makes RSVP an appropriate option, but since it's casual and mostly family, and since my Dad mentioned being reluctant to make people RSVP(no explanation), I'm looking for an alternative.
But the main reason I'm concerned about what to say on the invitation is that, in my experience, people ignore RSVP anyway. Also ignore Regrets.
What can I say on the invitation so people actually let us know if they are coming?
"Please call us by May 1 if you cannot make it" ?
"Please call or email to let us know if you are coming" ?
"We look forward to seeing you, if you or any of your family can't make it, please call and let us know before May 1" ?
How much can I spell it out without insulting the people who actually know how to behave?