Thursday 4/30 is also a Grad event, so don't rearrange plans to that day
I really don't know if the Grad events will impact
Epic crowds. Epic wasn't really open during last years' for comparison (it was just in previews).
Really, Epic is still pretty "operations" dependent and variable, You could hit low crowds but the rides are having a rough day and most lines are long. Or you can get a busy day with everything operating and you would do more that day. So I would really plan Islands when you want it and just throw Epic whatever day you've got left.
Just make sure you can hang to the end of your Epic day, when those lines all drop and the park is lit up beautifully.