I think the T-Giving crowds will be heading home at the time you arrive but I'm no expert on that. I have been going at this time for the past 3 years and I enjoyed myself. With all of the talk about this being a good time to go, I think more people head down and thus, the crowds are probably a bit larger than in year past. BUT, it's a great time and even though the weekends can be hectic, I have never had a problem with horrible crowds and the lines for the major attractions usually aren't that bad. Since you will be there just during the week, I think you'll be fine.
A couple of years back, I was able to stay on Splash Mt. for a 2nd ride without having to get off due to there being absolutely nobody in line when we came back into the station from our first ride on it. And that was on a Saturday around noon.