Out of Sun/Mon/Tues, Id go to Magic Kingdom on Tuesday. Sundays are extra magic hour, and parks tend to be more croweded on their EMH day! A Disney book I have said that traditionally, Mondays are very crowded at MK. Id go Tuesday!
Miss Magnolia- Ive also heard on these boards that the weekday showing of Specto causes that day to be a bit more crowded. Im not sure how crowded it will get at night in January just for the locals to see spectro. I bet thats more true in warmer months. Your plan sounds good though! Just hop over on TUesday after Animal Kingdom, see Specto and Wishes, and go back the next day!!!