I agree with some of the other users since they are not into the thrill rides and like music MGM and AK are great first choices.
MGM = Beauty and the Beast, Fantasmic (at night), Voyage of the Little Mermade (all three with music) but also other great shows like Indiana Jones, Lights Motor Action and the Muppets 3-D. They also might enjoy the Great Movie Ride.
Ak = The Festival of the Lion King, Pocohontas and Nemo are musical shows but then you have Flights of Wonder and It's Tough to be a Bug. Plus you could go on the Safari and to Conservation Station.
MK = Mickey's Philharmagic (Not to be missed) plus too many great dark rides to mention that are a lot of fun and you can't go to WDW and skip the MK.
If you have to split a day up. Choose a day when MK is open late, go to AK in the morning/afternoon and then MK in the evening. Then the other day MGM in the morning/early afternoon hop over to Epcot and tour the world showcase for the afternoon (maybe try to get on Soarin or Nemo) then go back to MGM and do the Fantasmic dinner package.
Any more days you have you can go back and do things you loved or missed.
Have fun! Bring good shoes!