What is best way for 3 person family to share 200 gb music on 1 itunes account on two networked windows 7 PCs, have access to each others music on each PC but have own libraries. Goal is simplicity

Question

Currently, one windows 7 pc is upstairs in common area and is used most frequently.  Father's (me) windows 7 pc is downstairs and has 200gb music collection on internal hardrive.  PCs are networked together.  Wife and kids would like to buy and listen to itunes music upstairs.  They would be ok sharing a music library and it would not need to be huge.  They generally, but not exclusively don't care for my music.  I am eclectic and like their music as well as mine and would like access to it to be able to easily put it on my devices for family trips, etc and update playlists. 
Ideally, I would like to be able to keep all of the music together on the same hard drive for managament purposes (organizing, replacing a computer, etc).  I don't trust them not to screw up my library (too many hours invovled in it already), so I'm assuming that they should have their own libraries.  These they would access upstairs and would also sync their devices on the upstairs computer.  I think both their libraries could be pointed to the harddrive on the downstairs computer where the music files currently reside.  When they played music from the upstairs computer, it would play from the downstairs computer across the network.  If they purchase music on the upstairs computer, I would like it to get downloaded on the downstairs computer with the other music files and not be downloaded onto the upstairs computer.  I would like to be able to rely on my library and the music files not getting messed up.  If friends and babysitters come over, they use the upstairs computer.  We've had a disaster before when it was just one computer, but the music was on an external hard drive and my wife launched itunes without turning on the external hard drive first and fried my library.
The best I can come up with is their having their own libraries, on the upstairs computer, that reference all music files on the downstairs computer over the network.  Am I on the right track here?  How do I make sure their purchases go into and only into the music file downstairs?  Is there some other better option of having a separate itunes on the upstairs computer and storing their music separately upstairs?  How would I make sure to get copies of their music files from the upstairs computer also into my large music file downstairs, so I can keep one comprehensive collection of music all in one file.  This seems like it shouldn't be so very difficult in the 21st century.  I ought to be able to keep one comprehensive music file and one comprehensive library, even though my wife and child, who are less computer literate than me would like smaller, more personalized libraries and to purchase music on the convenient upstairs computer and even store their music on the upstairs computer accross a network.  I the old days, you could just dupe some of the CDs.  HELP!!!!!!!!!!!!!!!!!!!!!!  My wife is tired of waiting on me to resolve.

Answer 1

Anything Downloaded with a Particular Apple ID is tied to that Apple ID and Cannot be Merged or Transferred to a Different Apple ID.
Apple ID FAQs  >  http://support.apple.com/kb/HT5622
SHARING iTunes MUSIC
http://macmost.com/five-ways-to-share-music-in-itunes.html