Just called the hotel.
1) There are at least 9 king bedrooms available and 9 double bedrooms that are bookable with points/anniversay nights. I say 'at least' because the reservations agent wasn't able to see all the rooms, just "at least 9 per each room type".
2) The events manager is going to look into the possibilities for the Shabbaton. She said there are a few events going on that day, with several caterers working in the kitchen. She said we would have to bring a caterer in (they have a few they've worked with in the past) to cook there - they don't allow outside food in - but even so she has to see whether there is room for another caterer to be working in the kitchen. I suggested the idea of having a caterer prepare food at an outside facility and just warm it up in the kitchen, and she said she'll look into it. My idea with the last one is to buy POM food and have a DDFer be a "caterer" who officially supervises the kitchen work.
3) Didn't even discuss parking yet.
4) Event manager will also look into how many rooms are booked for Saturday night. If it's quieter (which she said is usually not the case), then we can talk about staying in the rooms till Shabbos is over. Obviously, checking out at noon and leaving bags at the front desk is a possibility, but that would mean no naps and everyone would have to hang out in the lounges/conference room all day... How long is that "all day" on a Winter Shabbos by the time the meal is done? Probably not very long.
If Shacharis is at 8:30/9 and done by 10:30-11, you send everyone back to their rooms to pack while a few set up lunch. Lunch at 12 (which is checkout anyway) and it's over at 2-3. You Daven Mincha and chill for and hour and then eat Shalosh Seudos and it's over. Unless we have babies that need naps, checking out at 12 might not be such an issue. If only a few people have kids that need naps, it would probably be easier to convince them to let us keep 5 rooms till 5PM than 20 rooms.