I have been to Disney several times over Thanksgiving week. The last time it was so bad I vowed never to go back at that time of the year. It was so crowded we could not walk. My son was holding my hand and just got ripped away from me by the crowd moving in the other direction. The buses were so packed you could not breath and the lines were forever.
If you have your heart set on going over Thanksgiving, Liberty Tree Tavern has a traditional Thanksgiving type meal that is quite good. Some of the other places do also offer Holiday meals. Also keep in mind that holiday pricing will also be in effect so everything will cost more. Hope you have a great trip.