Add to the sudoers file (/etc/sudoers) an entry like
user ALL=(ALL)NOPASSWD: /sbin/shutdown
Where you replace user for the username of the person who want to allow to be able to perform this task.
the user should be able to then do '/sbin/shutdown now' for a shutdown or '/sbin/shutdown -r now' for a reboot.
this might be a good source for sudo as generally sudo doesn't change between distributions from what I have seen
As for Hard Drive quotas that's really a completely seperate issues and will likely involve changing /etc/fstab. I think more information might be needed for the hard drive quotas and that it should probably be an issue for a seperate thread as having two issues in a thread does run potential for the issues to slightly conflict.