Here's some pictures of Chase making the cards.
He loved it. I used Crayola washable finger paint. On the inside of the cards we wrote a message to each grandma and also tacked a picture of him creating his masterpiece. 

Before you start, make sure you have a bath ready for when the project is over (clearly baby gets really messy.) Also the paint did not wash out of the sheet, so I guess that will be my arts and craft sheet for now on.
Voila, the finished project!