ITunes For Mac :: Moving Media With Multiple User Libraries?

I am running out of room for all my music, movies etc, so have purchased an external drive for all my media.  

All files are currently under the "shared" portion of the hard drive. It is set up so that different users are accessing different files in their libraries (eg my husband has his music, I have mine), but none is accessing everything. We had it like this to make it easier to manage our individual iphones, ipads etc, without having tracks that we both use duplicated in the hard drive. And its been great. 

My problem is that I now want to move all the media to an external drive, and everything I have read recommends doing this through the itunes library. I am concerned that only one persons stuff will be moved by doing it this way, leaving the other missing files. If I simply move the folder, will it work to just point each library to the new destination? Some things I have read indicate that this won't be successful and that itunes won't find the new files.  

Also, a small(ish) thing, while I am at it I would be quite keen to implement the new file organisation system with Music, Movies etc all on the same level. But not sure when or how to go about that with this setup. 

Am I best to set up a new user, and import ALL folders into itunes, then move it within that itunes? Or should just moving the folder and pointing each itunes to the new location work?

Info:
imac, Mac OS X (10.6)