Weather could honestly go either way those dates. BUT, visiting the first week of December is my absolute favorite time of year to go. The Christmas decorations are BEAUTIFUL and many of the characters are dressed for Christmas, too. And, the crowds are low (but the parks do close early many days, so if you prefer to be there late that's a problem).
Also, it's "value" season at the resorts, so if you're staying on property you can get a great deal.