NYE is considered a holiday and when you make a PS at 90 day mark(and I definitley recomend doing this!) they will ask for CC, but you can cancel 48hrs before. We have spend last 2 NYE in WDW. 2002-3 we ate at Tewppanyaki in Epcot and last year we ate at Brown Derby in MGM. We were able to park hop between these 2 parks on NYE, but if you plan to go to MK, I suggest you go early(it has closed to all guest including resrt guests by 10am both years) make a PS for the park at 90 days (if you leave the park for resort dinner, you may not get back in) and plan to stay there until midnite events. MGM, Epcot and MK have fantastic fireworks at the conclusion and MGM had 3 shows of Fantasmic that night along with Fireworks. Epcot has a special Rock and Roll NYE party the last 2 years at the Millenium village building with buffets, live music and kids/adult activites. It cost extra and you can go to Epcot stuff and return. Swan/Dolphin also have similar event.
Connears