Need Help with Gender Reveal

I live far away from family but we still want to do a gender reveal. My husband and I know the gender (girl). So what I need help with is I found a design which I love. this is a 20x20 poster for 21 dollars. I'm thinking my husband and I will take a picture with it and post it to social media and send out a text. my other idea is: this design comes in 4x6 mail-out-cards. I could order the cards and mail then to everyone. however I'm not so sure I like that idea because I'm worried people will get them at different times. which should I do? poster or mail out cards?