Earlier, I started a post on how to announce a baby is coming to your loved ones...
hopefully over the coming posts, you'll find some of this tidbits helpful.
Big Family Gathering
Gather the family and let them in on the secret by giving them a shirt with the iron on saying "What are you looking at GRANDPA & GRANDMA" and you wearing a "Yep" it may take a minute, but eventually he'll get it!
If you've got the funds, think about getting an announce up at a game. Either pay for the big "Hey dad, we're pregnant!" for the scoreboard, or bring your own sign and open it up for the cameras to catch (bringing you on the screen and he will suddenly see it's not "Go Mariners" you're holding).
"Hey I need your help with the car..."
Stop by your dad's and get him to help you with something in your car. Let him know you are trying to install a new gadget and it's just not working. Once you get out there, open the back seat and let him "see" the new gadget....a car seat.
Surprise your parents with a card "just because" and inside, place a gas gift card. Explain to them... you'll be needing this as we'll be needing you to come visit your new grandchild!