phpMyAdmin, below, can admin users but I have never actually done it.
2) Getting users actually connected to the database.
Users can connect from a client on their PC/workstation, but this has problems because you dont necessarily want to run MySQL with a port open to the net, it should just be serving the local Raq websites.
Users can login to a shell on the local Raq and run the mysql client from there, but that means you would be giving them shell access, which might not be part of the plan.
I reserve each Raq's root website for MRTG stats and other per-user things and install phpMyAdmin in one of its subdirecetories. It uses the MySQL db/table access permissions to implement a basic http login to a pure web interface to MySQL. A user logs in and all they can see/modify/etc. is what MySQL is set to give them. They can do anything they need to, including paste in scripts and download dumps, etc.