Planning a group family trip for Dec 26-31,2013 and not sure how soon to book. We have a tentative head count of 10 adults but that could change. Is it better to book and then change if necessary or wait til more definite on people? I have been to WDW lots but never during this time (I know it will be BUSY but only time all can go ) Probably gonna book 3 Value rooms but looking for suggestions that aren't too expensive since some are on a lower budget. Never booked and cancelled or changed so what are fees if any? TIA!!