The suggestion about leaving Magic Kingdom for Epcot to have dinner is actually very reasonable if you have the time and you are looking for upscale restaurants with more appeal to adults. Another couple of possibilities along those lines: Take a boat over to Wilderness Lodge, and go to the Into the Woods or Enchanted Forest (or some similar name) dinner at Artist Point. The food has been outstanding when we have been there. Great appetizers, cleverly served; excellent prime rib; very nice desserts including the "poisoned apple." The character interactions are excellent: Grumpy, Dopey, Snow White, and especially the Queen, who is a master of comedy. The lighting is also very special, and it changes depending on the character action that is going on.
Another alternative is to walk or take the monorail to a restaurant at the Contemporary. Chef Mickey's is there, and we have always found it enjoyable. For our last night at WDW, we have often gone to the California Grill. It now has a prix fixe menu, which we like a bit less than the a la carte menu of the past, but we have enjoyed it quite a lot. You have a spectacular view of the Magic Kingdom, and if your dinner time overlaps with the fireworks, you can go out on a balcony to watch the fireworks, with the music playing.