Why not just take a picture? If you're interviewing so many people that there's a genuine risk of forgetting who is who, a picture seems useful. I'm sure I'm not the only person who will forget your name in 3.5 seconds but never forgets a face.
Maybe this is my time at Pivotal speaking, but your first day on any team you get your picture taken with a polaroid. It goes on the pairing board. It's not weird.
"Thank you for interviewing with us! Mind if we take a picture so we can keep our who's who straight when the team is making the decision?"
All that jazz with IDs sounds unfriendly, sure. A snap isn't. Hell, make it a selfie with a team member.