How did or will you tell the grandparents?
From Amazon I purchased sonogram picture frames with a really cute saying in it.
http://www.amazon.com/Grandbaby-Ultrasound-Tabletop-Photo-Frame/dp/B006I6U2UI
For his mother, we're telling her on grandparents day and I'm going to give her a gift bag with sonogram in a picture frame.
A week later we're flying out to visit my mom and dad. I'm going to give them a lime or a plum (which is the size the baby will be when we tell them) and ask them if they can figure out what it symbolizes. And after they've driven themselves crazy, I will give them the sonogram in the picture frame.
Oh yeah, and I bought a card for each of them.