I don't know what the park hours will be like that day, but hitting four parks will be tough. You'll lose at least a half an hour between each park. It easily takes a whole day to see MK. The major rides at AK and MGM can be done in less than a full day, IMHO, but Epcot also requires a full day. If I were you, I'd consider hitting two of the four instead. Having said that, in the middle of a week long trip, on a day that started at 7am and ended at midnight (EMH) we once hit the highlights of three parks in one day. Primarily we were at Epcot for the day, but on the backside (WS) we took the boat to MGM to hit a few things there, then after Illuminations (the best fireworks show at the time), When Epcot was closing, MK was still open for another 3 hrs. so we hit a few of the rides there. IT also depends on the crowds. On April 8th, if the crowds are significant , it may be difficult to get through the rides quickly...If you are hopping between parks, it also makes it hard to use the Fastpass system.
