if today, May 5 I want to book for December 5, can I book the entire reservation if I wanted to stay Dec 5-12 or only one day? Meaning do I need to wait until the 12th to know I can get the full week at the same resort/room?
You can book up to 7 nights from the checkin date, so today you can book a stay that checks in on 12/5 and checks out on 12/12. You can add additional nights one at a time day by day (add night of 12/12 tomorrow, etc.).