One of the first things I checked into when I got local Internet (no long-distance call) was IRC, which was relatively new at the time. Before long, though, I was onto boards like the old SF site and chat got left behind. I think there was a resurgence of interest in chat several years ago and maybe there is another wave today.

I was introduced to Pidgin a while back. It is essentially a chat client that works with a wide variety of IM networks. You guys could try it. Download the software from here and install. You can exchange addresses on AgTalk, if you like. That way, only AgTalkers will likely join your group.

If this isn't what you need, let me know. But it would be simpler from an admin standpoint. Much simpler.