Call every day, or twice a day if you can. Take any part of the time you want that they have - you can cobble together a reservation over time. I've had to do this a couple times for Thanksgiving and Spring Break, and I always ended up getting what I needed, sometimes one night at a time. This year I made my T'giving reservation way in advance and we might have to cancel, although I won't be sure until it gets a lot closer (fingers crossed that we can go!). I think a lot of people make reservations even though they're not sure they'll actually go, because it's easier to cancel a reservation than to get one during popular times. When these folks get around to cancelling, you might pick up the dates you need.