Hi Leeann!
Christmas is my favorite time to visit Walt Disney World and not just for me, but my son (3) loves it too! The entire resort is beautifully decorated for the holiday and the Christmas spirit is everywhere. Your kids will love seeing Mickey Mouse dressed as Santa Claus. You can even have their pictures taken while sitting on the real Santa's lap! While the park may be crowded, I think it is definitely worth visiting during this time.
One of my favorite things to do during Christmastime is
Mickey's Very Merry Christmas Party, which is a separate ticketed event where you can walk down Main Street in the snow! You can enjoy complimentary hot cocoa and cookies all night long, dance the night away with the characters, and still enjoy all of the attractions. This event is limited in ticket sales, so the park doesn't get too crazy crowded.
You can also resort hop to view some amazing holiday displays, like the life sized gingerbread house at the Grand Floridian and the floor to ceiling Christmas tree. A family photo here makes a GREAT Christmas card.
Happy holidays to you!
Leslie