It's not busy earlier in the month but gets busy closer to Christmas. Then it is terribly crowded from Dec. 26-Jan 1.
They have Grinchmas for the kids and Macy's parade during the day. The parks are decorated for Christmas from around Dec. 10-Jan 4th or so and Christmas music plays in the parks. Suess landing is expecially fun to see with the Christmas decorations and the Grinch.