IF the grandkids have Grandpa's truck title and it was pulled out of the field without their permission (which would be the case cause they still have the title), they're going to be happy you restored it for them! I know the chances of this actually happening are slim to none, but stranger things have happened.
I know two people personally that this happened to in the last 15 years. Neither one bothered to do the DMV paperwork until after they spent the time, money, and effort on the restoration.