I would definitely visit the Grand Floridian. What you might want to do is plan to just take the monorail around and stop at each hotel. They all have some nice decorations. Everyone says the WL has nice decorations, too, but we haven't actually seen them.
You might also want to consider making the trip to DTD. The decorations there, especially at night, with all the lights are really pretty.
As far as the other hotels...the Dolphin typically has a huge tree in the lobby area. And, the YC/BC and Boardwalk all, in the past, have had nice displays with gingerbread houses, trains, etc. They are nice to see.
The moderates typically don't have as lavish of decorations as some of the deluxes so those would probably be only if you get a chance.
Of course, don't miss the Osborne lights. They are absolutely beyond description. You'll enjoy the season. We love it there during the Christmas season.