I am a lurker, but thought I might be able to help.
Our daughter was married at the pavilion June 14th. Our sales manager told us a year out (and before we signed the contract) to try to get an idea of how many people we would be planning for, because the contract is signed based on that. Through our conversations with him, we realized we could not just "guess." We sent a "save the date" letter out a year before the wedding and asked for a response. We included a reply card with a stamp, asking people to give us an idea of whether they would like to join us for their wedding. We gave three options: yes, we would like to plan to attend, count us in; no, won't be able to attend; not sure - keep us informed. Based on the replies we received, we signed the contract with Disney. We had to guarantee 75 room nights. We more than met the requirement. Yes, we were scared to start with - 75 room nights seemed huge. Our sales manager assured us with the number of people we were expecting, we would have no problem meeting that requirement. We had 120 guests at the wedding, and quite a few people stayed off-site. However, it didn't take long to get the 75 nights, since most people came for the wedding events and stayed a few days for vacation. We did select a hotel from each price range: value, moderate, and deluxe. We thought for sure most people would stay at the value resort. We were surprised at how many people stayed at the moderate and the deluxe choices. FTW even counted DVC member rooms toward the grand total of room nights! So, plan ahead and underestimate. You can always add to your count.
We had a dessert party for Illuminations and at first thought we should take the smaller terrace (smaller minimum number of people.) However, once we heard back from our guests, we had to switch to Italy terrace because we needed the larger space. Also, if anyone used a park pass or had APs, they will not charge those guests the viewing fee.
Our daughter's wedding was everything she hoped for - and then some! It was great working with FTW - we were able to relax and enjoy the entire weekend of events! Good luck and happy planning!