There's probably various ways of doing it but I am wondering if the best wouldn't be to simply copy the entire library as it now stands to each of their computers then delete files on each computer to personalize. This has the advantage that the iPods would still be syncing with their "old" library and won't need to be erased as they would if you create a blank library on each computer and transfer individual files.
Moving a library: Quick answer if you use iTunes' default preferences settings: Copy the entire iTunes folder (and in doing so all its sub-folders and files) intact to the other drive. Hold down the option (alt) key (shift on Windows) and open iTunes. At the prompt to create or choose a library choose the copied iTunes folder.
When this is to a new computer put the copied iTunes folder in the default location of Macintosh HD > Users > *User Name* > Music then you don't even need to start with the option key held down, iTunes will automatically look for it there. (Make sure there isn't anything already in the iTunes folder there that you want to keep since you will be replacing it with the one you are moving.)
If you wish to continue to share media you can try various option of Home Sharing and Family Sharing.
Family Sharing - http://support.apple.com/kb/HT201060
Sharing purchased content with Family Sharing - http://support.apple.com/en-us/HT201085
iTunes: How to share music and video - http://support.apple.com/kb/HT2688 - about Music Sharing and Home Sharing
Home Sharing Support page - http://www.apple.com/support/homesharing/
iTunes: Setting up Home Sharing on your computer - http://support.apple.com/kb/HT4620
Understanding Home Sharing - http://support.apple.com/kb/HT3819
