Map voting is now enabled, so you can change map/mode without an admin online. All you have to do is press "x" in game and either double click on a current vote or select a mode/map and then right-click and select "vote for this map".
Just to be clear, the server will not keep running after this week. Right now it's on a standard EC2 instance, so I'm paying by the hour. So on Sunday around midnight (UTC) it will shut off.
As for mods, I'm not sure. I set this up to run an as identical server as the one they will be running during TNT so people could practice. If they are going to run mods then sure I'll add mods. However, just have to figure out how first.