/agree with Sam.
The TF boards remain available to those that have left the game, changed servers, etc.
It's been nice to be able to keep up with my friends there despite the fact that I don't play with them anymore. And there's actually as far more discussion in the general forum than there is in the private forum (by a 3:1 ratio).
Internal politics, specific prayer requests, and inside jokes typically take place in the private forum, where people aren't afraid to use real names, explain the situations.
The hardest part will be getting everyone set up and added to the list. If you decide to do it, please be patient with the forums admin that has to set it up. You guys are a rather sizeable group of people and it'll mean a lot of time getting each profile updated.