I started a small Mastodon instance for about two dozen people who all know each other (from Google Plus). Is there a way for all of them to see the handles / profiles of all others? As a seconday question, is there a way for me as an Admin to message all of my local users?
No, and no, respectively I am afraid. Only if you guys are active on the local timeline. Some people do workarounds by keeping a list of all local users.