I recently changed some of the settings on the discussion group
to allow all members to invite other people. Once you've joined the group, there should be an "Invite" link on the main group page. Of course, you can still just refer folks to the main group page directly, as before.
Also, I've added the group to Google's public directory, so it can be found by someone searching for "Danville 1996
" or "Danville Indiana reunion
" or other similar queries. The posts are still members-only, though.