help with Christmas announcement?!

I posted this before but only got one response. My fiancé and I have a 2 1/2 year old together and want to incorporate him in the announcement as well. My fiancés family will be visiting and having dinner with us at our place on Christmas <a href="">Eve</a>, so that's when we plan to tell them. Then my family we will tell Christmas Day when we go visit them. I want it to be a cute unique unexpected way because I doubt we ever get another chance to do a Christmas announcement! Currently there is a picture of the three of us with our son holding a sign and I edited onto the sign, "pink or blue either will die mommys due with baby number two august 2017" but that's not very Christmasy and the picture is blurry and I'm not sure if we will be able to have someone else do it before Christmas, we also have one where it's just our son holding the sign, he's looking at it with a Santa hat on and I edited, "merry Christmas to me, I'm a big brother to be august 2017" but I don't think I just want to hand them a picture and that be it, I want to have a scavenger hunt or tell them some other way but still give them a picture to go with it. The only thing I have thought of was for my fiancés family because his mom will go nuts! Lol, was too write on a piece of paper as if t was a recipe, "Preheat oven 40 weeks, insert bun, set timer for August 2017" and I want to hand it to her while we are making dinner and ask her to make this for me. I think her reaction would be priceless, but I'm not sure what to do with my family to tell them. My mom I could probably do the same thing but my parents aren't together and we won't be having dinner with my dad so that wouldn't work lol.