Beautiful
Jokes aside, a quick search shows that pinterest is filled with these type of game ideas. Personally, this would be a better topic for tumblr. just post the question, no context, also remember tags for maximum exposure.
https://www.pinterest.com/explore/gender-reveal-games/
Put a video of a box. You and your baby momma open the box and a colored balloon opens. Pink for Girl. Blue for Boy.
I'm glad the warhammer chaos gods are on that thing. That makes me happy.