For AK:
If you can swing it, take the bus to Animal Kingdom Lodge while you are at Animal Kingdom park and go to dinner at Boma. It's a very quick bus ride - just a few minutes. It's a nice thing to do at the end of the day at the park. You can relax by the fire or walk outside to check out the animal viewing areas. Then go for dinner at Boma - they have a great buffet. A good mix of African inspired dishes and regular stuff like prime rib, roasted potatoes and veggies. The desserts are out of this world. They have a good salad bar and a kids buffet with mac and cheese, spaghetti, chicken and fries.
MK: CRT for dinner (no characters). We loved it. The prime rib is very good as is the caesar salad. For characters, we liked both the Crystal Palace and Liberty Tree Tavern alot. I would suggest CP for lunch and LTT for dinner.
MGM: We just haven't found a place we love there yet. We liked Sci-FI for lunch. DH hates Prime Time because the schtick of the servers annoys him. Hollywood and Vine buffet for dinner was okay - nothing to write home about. I would suggest maybe trying a Boardwalk area place for a TS.
If you would consider going to a resort restaurant, I highly recommend Kona Cafe at the Polynesian. It's a great deal on the plan - our bill for two adults and one 3 year old was about $119 and we paid $80 for the whole day on the plan that day. The food was outstanding, including amazing desserts. Just a quick monorail ride from MK.