I was at the Super Bowl in 2001, the last time it was held in Tampa. Of course I did a follow-up day at Disney's Hollywood Studios (then MGM) before heading home. You can read about my experience with this
HERE. I have also been at WDW during MLK weekend twice, in 2007 and 2008. You can read about this
HERE. In addition to my previous comments I will say that while there may be an uptick in attendance on the day on either side of the Super Bowl, the parks are likely to be fairly dead on Super Bowl Sunday. Most folks will be holed up in a hotel lounge, the ESPN Zone, or their room watching the game.
In a nutshell, despite any special activities, all of January will have much lower park traffic than any weekend in the summer or any time over the winter holidays. There is some event that will add traffic to the parks on every January weekend in 2009 except the 24/25th. (In addition to the events you mentioned, the Disney marathon will take place on the weekend of the 10th.) So, for the lowest attendance weekend at WDW, shoot for the 24th as you focal point.
Hope this helps.