My suggestion would be for each person at the autograph session to have a name plate in front of them so you know who they are. Even a printed up list of the games they have worked on would be nice.
No offense, but it's not like pinball designing is a job that makes you a recognizable person (like an actor or sports star). A lot of designers are really admired for their work, but I wouldn't recognize many of them if they would knock on my door and ask me to loan them some Novus 2.