If you activate the collaboration mode for your public boards, your visitors will now have more options to collaborate with you. Among others they now can switch status, close tasks, see closed tasks, attach files and more.
Keeping your colleagues notified should be easy. On the bottom of any activity you can now make your colleagues to followers and so keeping them notified about changes and comments. Your team mates will now also become automatically follower if they add comment to activity or if they become assignee.