We go every Easter week and it is extremely crowded. This year was the worst. However, that is the only time we can go because of the school calendar. Just do a lot of planning.
The MK closed for a couple hours during the afternoon a couple days; the waterparks are filled to capacity by 11:00 am; fastpasses for a lot of rides are gone by early afternoon; at 11:00 am Test Track had a 120-minute standby line.
Stay away from MK on Easter Sunday. The other parks should be fine.
We always try and go early to the parks, leave by 1:00 for our rooms, and then return at dinner. The parks are always open quite late, and there are two showings of Fantasmic and the Spectro parade. (Always try for the second showing of anything.)