mommyoeo, you might want to actually call them anyway - I was just reading on the camping forum about the campground being booked already for next year (which is what I based my last comment on) but there were also some folks who called recently and got dates in December. That's when I remembered that WDW only allots certain rooms and campsites to the web site for booking, so there may actually be availability, but it won't show on the web site. You can call them for a quote and not be obligated to buy! But, with the campground so popular in December and apparently filling fast, you may want to decide sooner than later.
Again, good luck!