I think it depends on what you're interested in. I'm interested in consulting, and I wanted to find out more about the alumni network, the value of CBS in Asia, etc, so I picked an older alum (1976 grad) based in SE Asia who's worked in consulting all over the world, and whose 3 kids all are CBS grads. There were other younger alums, but I chose the one who best met what I was trying to learn about CBS.
Maybe you should figure out what you want to find out/ask about CBS and try and google the available interviewers to see who would best be able to answer them your questions.
My $0.03 (inflation adjusted)