Out of town birth announcement

So my hubby and I have been brainstorming how to tell his family (who is local) that I am pregnant with our third...and in the mean time he came up with a way to tell my mom (who lives out of state) we are going to send her a picture of an airline ticket and the sonogram picture and tell her she better ask for some time off work. We are going to buy her a ticket to come down once my hubby goes back to work. I'm so excited and j think she will freak out. 
I'm still stumped how to tell his family, we are having a get together (his parents, sister and brother in law)  Sat evening so I need something quick...any suggestions ??