I had the same thing. I wanted to tell my parents, but DH didn't want me to til we could visit his parents (a 5 hour drive, then a 1 hour commute between them, then a 5 hour drive back... usually about $300 in gas) so we had to wait until we could go see his.
When you do finally tell everyone, they won't care that you waited to tell them. It was my parents first grandbaby (now twins) so, relax... no matter when you tell, they will be excited.
And if you and your mom are close, I'm sure things will be fine. no need to ban everyone from the room!
Just remember, there is a beautiful thing inside of you right now... and its going to mess with your emotions SO FREAKING MUCH.