Gender reveal blues 😔

Renee • Mom of 3! Expecting #4/DH's 1st. October 2015
So this is probably my last baby (4th csection) and it's my guys 1st so I really wanted to do a gender reveal bbq. My sister offered me her house to throw it but stated she was busy every weekend in April... Bummer really wanted to do it next weekend but hey I can't be upset right. So then she emails me asking me to wait tol may 24th because my niece will be in town and it's my sisters birthday. What!!! If I waited that long I might as well wait until my guys birthday which is on May 31st right.?! And I tell her that and she said just pick ur own day and I'll see if I can make it. Everything always has to revolve around her. I told my guy I just didn't want to bother with it. Let's just find out together when our tests come in and we can take some cute pics and text it to our families next weekend.am I wrong in not doing it around her schedule?