SAWYERMAW - They can pull up your grandson's AP in the DQ computers with his name, birthday, and address. He'll just need to show up, spout off that information to the CM's at the ticketing window's, and they'll void out his old pass and re-print it.
You should be able to do this at any Guest Relations center. Try the one at DQ or DD. We've lost our AP, forgotten them, or just didn't have them with us and decided to stop for the day and have never had a problem getting them replaced. Good luck.