The first week after the Thanksgiving Holiday until the week before Christmas are the best times. They are indeed the least crowded and the most festive. We plan our WDW vacation at that time every year.
Are as follows, 01/01-02/14, 08/26-09/26, 11/04-12/2 for all Value & Moderates, WL,AKL, and FW Cabins. 01/01-02/14 and 08-05-12/20 for the camp grounds. 01/01-02/14, 07/04-09/26, 11/04-12/20 for all other WDW properties.