maybe second child

so my husband and I have been talking about having a second child for awhile now. our son is 2 (turned 2 April 29th) when we planned to have him, we planned for the end of the school year. it worked out pretty well. looking ahead, I am supposed to ovulate August 13th which would give me a may 6th due date. and supposed to ovulate September 12th which would be a June 4th due date. I got pregnant with my son on the first try and thinking it will be easy the second time (this would actually be my third pregnancy, I had a miscarriage four years ago after our honeymoon) so asking other teachers and mom's which would be better? the may due date or June due date or try both months because I may not get pregnant the first try this time. ideally the closer to the end of the school year the better. I'll only have about 20 days of paid maternity leave. thanks in advance for your advice!