ITunes :: Setup Multiple Users With Multiple Devices?

I'm trying to find the easiest solution to our family music situation.  4 users, 4 devices (ipods, ipad, imac, pc laptops), and 4 different musical song interests.  I'm sure there are millions of households that have the same exact situation.  I want to be able to pull up only my musical library, not my kid's music, and then easily synch it to my ipod.  Everyone in the family wants to do this same thing.  I have spent alot of time trying to search the forums/internet and there does not seem to be one "most popular" solution.  I did setup iCloud for each family member using a different Apple ID than my main Apple ID, and I'm happy that ALL the music shows up on my ipad.  But between iCloud, MobileMe, Home Sharing it all gets very confusing.  Some say to setup multiple computer login accounts, and others say to setup 1 playlist for each family member and synch from that playlist.  

I would think 1 itunes account allows you to easily share a purchased song with 4 users, instead of buying songs twice. 

So here are a few of my questions-

1-Is it best to have only 1 itunes account and then synch all devices off of 1 main computer?   

2-Or since we each have iCloud accounts, will they be able to synch their ipods from their own pc laptop? 

3-And when they synch, what is the easiest way to exclude other users music in itunes? (other than unchecking hundreds of artists) 

4-Or setup 4 separate computer login accounts on the imac and then keep 1 itunes account?  If so, how does this work when they open itunes?  

Info:
Imac, Mac OS X (10.5.1)