Be sure to check out the list of rides open during the morning EMH at MK before you decide. When we tried it one year, we were disappointed to find that not all MK rides are open during EMH. Most of the ones we wanted to ride the most (Splash, BTMRR, HM, Pirates) were not open during the morning EMH. If I remember correctly, only the rides in Tomorrowland and Fantasyland were open that early. We were very frustrated, because we assumed that all of the rides would be open! Wished we hadn't gotten up extra early; it ended up being a waste of time for us.
But that was just us - it's worth a little extra research to find out what will be open, so you can make an informed decision. If your group is mainly focused on Fantasyland and Tomorrowland rides, then it's a good strategy!