We LOVE going in mid May, usually leave the middle of the second week and return the weekend before Memorial Day. Temp is mid to high 80’s during the day, although in 09 it was in the 90’s and HOT. Very rarely rains and crowds are low. We never took advantage of the am EMH only the night ones because we just loved being in the parks.
If you are going to go to the water parks, the waits are minutes if you go in the morning until about 1-2pm. We’ve never been there after 2 so don’t know how the crowds are then.