Activity for Tiara

How should I handle tentative RSVPs? I really need to start making certain reservations and there are people I invited who said they were coming (verbally or on social media) but, never RSVP'd even with a weblink provided. OR they did RSVP but I...

So a lot of hotels have the requirement that at least 50% of the rooms are booked. What happens in the event that less than 50% are booked? Does any one know? Do the make you pay for them?