Applications :: Saving And Syncing Music / Single ITunes Account With Multiple Users?

I bought an imac 24" 4 months ago and set up individual access accounts on the mac for me and my daughters. I then set up an itunes account for each and I started to pay into their accounts for them to purchase some music and all was fine after syncing each nano with their access account and itunes account.

However, it quickly became apparent that they could not share their music between account even though they are on the same computer. I have tried various searches but to be honest some of the methods suggested I just dont understand hence my appearance here.

Can I now save the music they have purchased etc and take it all to one account and then sync them again with the one itunes account or would i be better to keep the different accounts and change the set-up so that they can see and sync with each others music.