From personal experience last May, basically no restaurants are open during EMH in MK and MGM. I believe the candy store on Main St. was still open, and there was the snack booth with popcorn and drinks at the end of the main street in MGM, but that was it. As far EPCOT, I'm not sure, but since so little of World Showcase has things open during EMH, I am thinking the food situation there is quite limited as well.