i be there too 12/3-12/4 ... and i've been there that week before (2001)
christmas decorations will be full force ... expect some type of holiday cheer everywhere you go ... its beautiful to see.
all the resort lobbys at WDW are amazing ... HUGE trees and lots and lots of gingerbread. there's a lifesize gingerbread house at GF.
all the parks are decorated with trees and swags, and everything
MGM has Osbourne festival of lights which is a walk-thru exhibit of like ten billion christmas lights ... they have "snow" in the evenings at MGM
MK has
MVMCP ... which is a hard-ticketed event (extra $)
MVMCP has "free" hot cocoa and cookies, many/most rides are open, charcters are soem rides are "dressed (ie.. wearing a hat or scarf) two xmas parades which are worth seeing just for the marching toy soldiers and its snows on main street.
a few years ago there were special green and red fireworks but that was before Wishes so i dont know if that holds true ... also Goofy as Rudolph "flew" from the castle
its is an amazing time of year to visit ... it is also considered to be slowest time of the year at WDW ... i dont remember waiting much for anything and that year it was 80-degrees everyday.
weather in december could be down-right cold!
have fun!