We love making homemade gifts for family members. They mean more to us and it's the best keepsake to have from kids. Last year for my aunt, my kids Godmother we made her a special tag for the front of her car.
This is inexpensive and super easy. All you have to do is go to the local automotive store and get a license tag and cover. They cost less then $15.00 for both.
The tag I got had a flag on one side and blank on the other, so we used the blank side. The kids picked out the color for their handprints and place it on the tag. (Paint we used was just acrylic paint from Wal-Mart for $.59) Then used a sharpie marker to write the message.
The clear cover for the tag protects it so you don't have to seal the license tag.
The great thing about this tag is you can write whatever you want on it and you can design it how you like to. Personalized tags are not cheap and they don't have that personal touch with the kids handprints.