Hi, My family visited WDW the weekend before Thanksgiving in 2009 and 2010. In 2009, we stayed the Saturday before TG until the Saturday after TG. In 2010, we stayed the Wednesday of the week before TG to the Wednesday the day before TG.
The Saturday and Sunday before TG, the crowds were substantial in MK but managable. The Wednesday before Thanksgiving and Thanksving Day MK crowds are massive. The best strategy is to get to parks when they open and get fast passes for the most popular rides because they become more crowded as the day progresses expecially after lunch. In the morning, wait time for rides was very small, as the day progressed, it took 30 to 45 minutes for the most popular rides in MK. We love Going to WDW world in November because my children dont have to miss much school and because the weather has been extremely pleasant both years (even a little chilly at times). We usually pack summer and winter cloths and watch the forcast closely. We hope to go again this thanksgiving.