Congratulations! You're right ---- WDW at holiday time is extra magical, especially if you're someone who enjoys the holidays. The resorts are decorated beautifully, and it's fun to just resort hop and see the decorations, or plan to have a few meals in the resorts. Some of the favorites are WL and the GF, and the YC/BC and BW are also very nice. When at Epcot, you could just walk out the International Gateway exit by England and circle around to the YC/BC and BW resorts. Or take a boat from MK to WL or GF.
Mickey's Very Merry Christmas Party (
MVMCP) is a lot of fun ---- costs extra, but MK is just beautiful at night and the parade and fireworks are special. Even though the party doesn't start till ~7 PM, you can usually get entry ~ 4 PM, so there's extra time to enjoy the park. You might do that on a pool day or shopping day when you're not spending the $$$$ for park admission ..... or live it up and go all day long!
The Osborne Lights at MGM are turned on at dusk, and there's no additional charge. It's often quite crowded when first lit, and if you're planning to go to Fantasmic, you can view the lights after that show, when it might be a little less crowded.
There's a dinner package that includes seats to the Candlelight Processional at Epcot, but that's also extra $$$$. Guest narrators read the Christmas story and the choir & orchestra sing beautiful carols. If there's available seats after the dinner package guests have been seated, some people from the standby line might get in, but it's iffy and many people get in the standby line an hour ahead. (It's also possible to just stand in back of the open air theatre and still hear the narration and the music, but you can't see too well).
These are all the special holiday events that we've done. It's a wonderful time of the year whether you choose to participate in any of these or not. Just pace yourself.
Hope you have a spectacular trip!