Need help

So this Thursday i have an appointment with my OB for a follow up since I went to the ER Saturday for pain that I wasnt sure was normal or not (I have round ligament pain) so when I go to my OB and when she does an ultrasound and if she can see the gender of the baby Im trying to figure out if I should find out right then and there BUT I'm doing a gender reveal so I would only have the gender on a piece of paper that I'll give my sister, and the other problem is, is that my bf wont be there. So Im trying to think if I should wait on them looking for the sex and handing us the envelope or see if I can get it this Thursday. Any ideas? Input will be great!