I think you have a good time, actually. You can get up, go to the park as soon as it opens and get your Fantasyland rides done. You can eat a small "snack" before going. We are doing a late breakfast one morning, and I plan on having granola bars and fruit before we go. Once you've a couple/few rides, it will be time for breakfast. Depending on how much you eat, you will be good to go until sometime in the afternoon. We always just snack when we eat a late lunch. Then we have a nice supper. If you have another day to spend at Magic Kingdom, that might even be a good day to sleep in