Multiple users question

[John B. Thoo]

Hi.  I'm sorry if this is a FAQ.

I'm going to install OS X on our kids' iMac this weekend and, for the 
first time, set up OS X for multiple users.  (I currently use OS X on 
my TiBook, but I'm the only user.)  For what pitfalls should I watch?  
I assume that they will be able to share apps that are put in 
/Applications or /Applications (Mac OS 9).

Also, the kids, currently using OS 9, both listen to the same songs 
with iTunes.  With multiple users, would they still be able to share 
the same songs?  I ask because I note that my iTunes music is kept in 
my home directory on my TiBook.  I really don't want to use up disc 
space by having to have two copies of every song on their iMac, one 
copy in each kid's user home dir.  Please advise.

Thanks much.
---John.