Hi Doug! Epcot offers an incredibly diverse selection of restaurants, so this is a tough one to answer. A favorite choice of my family is The Coral Reef. The decor is amazing, but what really makes it magical is the chance to dine with the ginormous (my son's description) aquarium that makes up one of the walls. it is truly amazing to watch sharks and turtles swim by while eating.
Similarly, my sons like the Biergarten for the festive celebration throughout the restaurant as it celebrates Oktoberfest each day. We all love the chance to go up front and dance the silly dances, but just an fyi - you may be seated with other guests since the restaurant uses large tables like ones you would find at the actual Oktoberfest in Germany.
Another favorite is Teppan Edo. While we have a similar dining experience in our hometown, they still like the chance to watch someone throw knives around and play with fire while eating. It is a hit with small children.
I'd also like to throw out the suggestion of eating at San Angel Inn Restaurante with its feeling of eating in a small Mexican village, and it is a welcome break in the heat of a summer day. Restaurant Marrakesh is beautiful with a chance to try some more exotic menu choices (the kids' menu is traditional) and a do some belly dancing.
And finally, I can't overlook the Garden Grill to dine with some of the characters in a restaurant that actually moves!