The performers you bring up have excellent attendance records. To my knowledge Erivo has not yet missed a performance of The Color Purple. Danny Burstein is rarely ever out. The only time I can remember Audra missing is when a vocal issue came up during Porgy and Bess and she was required to go on vocal rest for a couple weeks. But thats rare (she did Lady Day without an understudy after all).
Also, considering its the weekend of the Tonys, I would think every performer on Broadway would do everything in their power to be on stage during that period. Unless, god forbid, some serious illness or emergency occurs, you will probably be fine.
As for seeing Javi, it may seem like a letdown not seeing the creator in the role, but I think you'll have a great time. I haven't seen him as Hamilton, but when I saw him during In the Heights he was incredible.