We have been the past 3 years for the week after Thanksgiving, and the busses have been fine. Rarely ever had to wait more than about 30 minutes for a bus. Granted, that is not as crowded of a time as when you will be there.
That being siad, when we go back this year, I'll be renting a car. The main reason is that I have 2 small children. They do very well in the parks, and stay up and happy till park closing, but as soon as they hit the stroller to go back to the bus stop, they are out. That leaves me and my wife each trying to hold a sleeping kid, and fold up and hold a stroller. Then at closing, the busses are packed, so we end up having to stand up while doing all of that.
I am looking forward to strolling the sleeping kids right up to the car, putting them in, and throwing the strollers in the trunk, and heading back to the hotel!