Last year in August there were some discounts offered by WDW for over the holidays but you had to check in by
December 23, 2006 - otherwise, it was holiday rates $$$$ all the way. So if you checked in on 12/23, you could have the deal rate for your entire stay, but if you checked in on 12/24 you paid the big holiday rate bucks.
But who knows what Disney will offer this year?

If they offer the same deals and you would end up saving lots of $$$, you might consider changing your dates and adding 3 days to your stay just to get the better room rates - of course also depending if you would save any $$$ after air change fees and if the air would even be available that is.
Good luck, and I know you'll have a wonderful time at WDW for the holidays
Last year Disney discount deals:
Check ins between 10/1/06-12/23/06 package discounts for Disney Rewards Visa cardholders became available on 8/14/06, exp 9/30/06
Check ins between 10/1/06-12/23/06 Annual Passholder room-only rates became available on 8/16/06, exp 12/23/06
Check ins between 10/1/06-12/23/06 Florida resident room-only rates became available on 8/16/06, exp 12/23/06
Check ins between 10/1/06-12/23/06 package discounts for general public became available on 8/17/06, exp 9/30/06
Check ins between 10/30/06-12/23/06 "available to anyone" room-only code became available on 9/28/06, exp 10/29/06
Check ins between 11/1/06-12/23/06 package discounts for general public became available on 10/2/06, exp 10/31/06
******