Oh jump in
Yahoo groups works well and is free, and allows you to use the calender so that group members can see what dates are free. You can set that up and not tell anyone for a while, till you get used to how to operate the website and all of its options. Our homeschool group runs largely as an e-group, with real life events as people plan them. No rules except that we try very hard to play nice. When we started we were the only secular option, now we are over 100 members. In our group if you want to say,have a field trip somewhere, you set it up and invite others, there is room for sign up sheet in the database area of yahoo groups, and place the event on the calender. The calender can be set to send out reminders for your event or class.
So far our group has...
met up for homeschool iceskating
have weekly playdates, that move so that they are never in the same park
set up a group of volunters to help at the soup kitchen
field trips to a farm, the firestation, the airport
gathered enough interested teens to hire a theater teacher
the hs teens have also taken over the librarys teen commitee
and found a knitting teacher who is willing to house a playdate at the same time
You could very easily do classes this way. And no pressure to have rules that say everyone has to plan so many events in a year...although as the group grows we are having pressure to become more "organized" but so far we have managed to resist. Good luck, have fun