We went down the day after T'giving in 2002. I had read how the week after T'giving was so empty, but didn't realize at the time that the weekend was still very crowded. Saturday was our first day in the parks & we went to Epcot, mainly because of our Princess Storybook Breakfast PS. We were literally the first people through the turnstile since our PS was for 8:30.
Overall, the park was very crowded, but not unmanageable. MS wasn't there yet, but TT was doable with a FP. World Showcase seemed more crowded than Future World. The only thing I didn't get to do that I really wanted was the Candlelight Processional. We did not book the dining package, because we were on the old Silver plan and we couldn't use it for dining. I thought I would be able to get in -- NOT. I did, however, sit by the Christmas tree in front of the American Adventure and listen to the whole thing. It was still beautiful, even if I couldn't see it.
Don't worry about the crowds. Just utilize FP when available. Make PS for your dining. And then go with the flow. You'll have a great time!