Hi Josh
I'm struggling to see how you can control anyone from using the volume control keys on the keyboard? This 'problem' might explain why you're getting little response to your question? That said you could set the mute setting and disable the sound control panel. But that would still mean anyone can easily 'un-mute' the sound by depressing the keyboard's volume control keys.
However a possible (clunky) solution you could try is to set the mute setting and disable the Sound Preferences Pane. You can use a number of ways to do this depending on what management solutons you have in place. Using ARD simply send a terminal command (man mv) that moves the Sound Preference Pane from /System/Library/PreferencePanes to any one of the local administrator's restricted home folders - Desktop, Documents, Library etc. Finally replace the Apple keyboards with keyboards that don't have the volume control keys - if such exist?
HTH?
Tony