Most of our wedding guests are coming from out of town, so FI and I have decided to host a welcome party the night before our wedding (the rehearsal and a small dinner with WP/immediate family is being hosted by FI's parents on Thursday night).
After venue shopping and cost comparison, we've selected a fun, casual place within walking distance of our hotel block that will serve heavy appetizers, as well as a beer, wine + soda open bar. That said, we live in an expensive Northeastern city, and the price pp is still quite high. We are inviting everyone who is invited to the wedding and are ready to host 100% attendance; however, I would like to know the actual head count as closely as possible (barring emergencies/travel issues/a couple of last-minute extras) so that we don't pay for lots of no-shows or unexpectedly have 20 more people than we were prepared to pay for on the day of.
My question is this: how do we politely intimate to our guest that this is a fully hosted event, and ask for a concrete RSVP? I've seen other threads suggest using word-of-mouth or the wedding website to communicate details, but that doesn't allow room for RSVPs, and I'm worried that if we send out separate invitations, people will get confused or forget which they've RSVP'd to. Our wedding planner has suggested we include the details on an insert with the invitation, and ask guests to RSVP to this event on the same card as for the wedding. Does anyone have any experience with this working out or any other alternatives?
Thanks in advance for your help!