End of April and the beginning of May is a quiet time after spring break.
The only thing you need to look out for in May is school field trips, but there's really no way to plan for that. I posted a thread last year of when my daughter was going, but only a few others posted when their school was going too. The good news about school field trips, is they usually don't arrive until 11am, and they have no way to get express passes. So again, the key tip is to arrive early before the busses show up.