Arranging Accomodations for Exclusive Use Inn

I am preparing for my wedding at the Bear and Bison Inn in Canmore (waiting for them to open up the 2019 dates so i can officially book) and one of the great things is that you get exclusive use of the inn and all 10 rooms (to fit up to 23 guests) for the weekend. The venue has said we can charge people for their rooms and then have them pay on their way out. Just wondering if anyone has dealt with this type of stuff before. We are inviting slightly more ppl than can fit in the inn though there are places next door. I have no idea how to coordinate this (first trying to fill the rooms we are paying for in advance waiting for reimbursement with checkout) and its stressing me out. Also tips on how to put this into a save the date as some people wont be able to stay at the inn.