My number one, all time favorite holiday activity, hands down, is the Candlelight Processional at Epcot.
The decorations at the Grand Floidian are beautiful, but so are the decorations at the Wilderness Lodge, Boardwalk and Beach Club. If you are going to the Magic Kingdom, the GF would probably be easiest for you to access b/c the monorail stops right there (if you get on the resort monorail).
Enjoy, it's just beautiful to walk around WDW during the Holidays.