Hi Tammy!
There's so many places to choose from, but my family always love the following:
Epcot
For dinner, two of our favorite restaurants at Epcot are Coral Reef Restaurant and Les Chefs de France.
At Coral Reef, we've always had a great experience there. The waiters there are super friendly, very knowledgeable of the menu, and pretty fast (like, say, on drink refills). The ambiance is pretty soothing, and the star attraction is...the Aquarium! Be sure to ask if you can get a seat near the aquarium. You can see the aquarium from anywhere in the restaurant, but being up nice and close makes it extra special. The Mahi Mahi and New York Strip are delish! Also ask them what the seasonal catch is, which is generally pretty good as well.
Les Chefs de France, located at France Pavilion, is also very good. Nice setting and good food. The roast chicken, and a particularly great creme brulee were my fave's.
Hollywood Studios
We absolutely love 50's Prime Time Cafe! The host will feel like "Mom," making sure you adhere to proper table etiquette. But they are a blast and are what really makes the experience so fun. We love the "time-warp-retro" experience with the black and white television shows and what-not. The food is very good also. The pork loin, fried chicken, and even the meatloaf are all pretty tasty. Don't forget to try the flavored sodas and speciality punches to "cap off" that diner experience.
I don't think you'd go wrong trying any of these. Have a splendid time on your vacation!