need advice! baby & bridal shower

 So my sister was supposed to get married in February, but due to personal reasons they postponed. 
I announced that I was pregnant at Christmas due in July.  Shortly after that they planned their date for June.  I will literally be 9 months pregnant. 
Some history, my sister has a habit of doing this, and my mom has a history of agreeing with her about everything. 
So, everything about this pregnancy is completely over shadowed by this wedding.  (Please note, she's 39 so this isn't going to be a huge affair)
I'm feeling really resentful and really trying not to harbour these feeling but I can't help it. 
So, this brings me to bridal and baby shower. 
I had to be the one to say we need to figure out the dates for the showers. 
So, this is my question. When should I have it?  I don't want the guests to have to have but two gifts so close together. 
Wedding is June 18
Due date is july 21 
And I have to tip toe Around mother and sister and make sure they're okay for everything.