I know that everyone has a differing opinion about EMH. We try to avoid the parks that have EMH that day because they are generally more crowded, longer lines for buses, rides, food, everything.
Our plan of attack is to go to park early, prior to opening, when lines are shortest, have lunch around 1:00pm and then head back to hotel for the hot, crowded part of the day. If we feel like coming back later in the evening we do, if not we don't. We normally plan our sit down meal in the evening at a resort that is closest to the park we will be at that day. So if we are at the park then we can just take a bus/monorail right over. If we aren't coming back to that park in the evening, we just take a bus to DTD and transfer to that resort's bus.
Also, if you have children please keep in mind that EMH can make for a LONG day at the park. Also, if you have kids, do they like to get up early or stay up late? Are you coming from a different time zone? That can make a big difference in everyone's attitude that day.