We sent the save the dates last month and had 7 rooms booked after that. I'm going to send invites this fall and expect most of the bookings to happen then. The RSVP will have three options, "coming and booked," "unable to attend," and "planning on joining, but waiting for a last minute deal" or something like that. Those are the people I will follow-up with. I also started a Facebook group and randomly post stuff there.