you can keep the group informed by post. You can also let other people post updates.
Make a forum.
You can create a forum in your group that other people in your group can answer other people's questions.
People can join your group.
People can join your group unless you put your group private then they come only in the group by invitation.
make a group page
Create a page with information on what your group is doing maintenance and ability to post blogs
Create your group and share it with other people.
A group is a page that you can make so if you want.
You can add a lot of things.
You have the option make a private group.
People can then come by invitation only.