How about both dates?
That will hopefully simplify things. I will make a "guest list" (subject to change, of course) so you can see who's coming.
There's nothing wrong with having 2 gatherings. If you can make both - great! If you can only make one, or if your schedule changes, then you can still meet folks. Or if it rains on Aug 17, then we have a backup.
Plus Rella gets to have visitors two times.
Everyone OK with that?