We have been late April early May before and are going on the 28th April this year also.
I honestly don't think it will be too bad, there will be times when the likes of Spiderman get busy at peak times of the day but generally I think the wait times will be manageable.
Certainly if you get to the parks first thing you should get on most rides at IOA in the first couple of hours without too much trouble.
Universal possibly a bit busier.
Late April/early May is a good time to go.