This is a fantastic idea!! I LOVE this!
If we did a Google doc, that would take the pressure off the organizer to manage the list all of the time. I think there does need to be an organizer who can divide the list into smaller groups, though. For example, if we had 30 people born in August, I don't know that I could send that many cards, and I definitely couldn't do that many on top of another exchange, like the summer exchange. But if the list were divided into groups of 4-6 people, I think that's reliably manageable. I think most people could probably send that many per month?
But we'd have access to the Google doc, so we could send to everyone that month if we wanted to and had the time.
Count me in if the number in any given month isn't too much to take on!