Moving kids accounts from my computer to theirs...

Question

Kids are growing up and I'm giving them their own computers, but their iTunes accounts, iPhones, etc., are still on my computer. I'd like to move these accounts and all associated music, iOS apss, and other media permanently to their own computers. I moved the oldest boy's account to his MacBook a few years ago -- don't remember how we did that, but it seems to have worked. Last year, I move all the middle boy's music and apps to his MacBook Air, but his iPhone, iPad, and iTunes account still show up on my computer and every time I try to associate them, his MacBook Air wants to wipe the iPhone/iPad and restore them to factory settings. He doesn't want to lose all the data from games, etc., on his iOS devices.
I'd like to simply move the iTunes backups from my computer to his, but something tells me that wouldn't work.
Is there an easy way to disassociate iPhones, iPads, and iTunes accounts on one computer and move the media, backups, and settings to another computer without losing any of the data?
Thanks!

Answer 1

Wow, lots of ideas! Thanks! To clarify matters, my kids do not have user accounts on my computer, just iTunes accounts, so Migration Assistant would be massive overkill and probably wouldn't even work for the purpose I have in mind.
On the other hand, my middle kid's MacBook Air has 128 GB of storage -- only have free at the moment -- and my iTunes library is over 268 GB, so copying the entire iTunes folder ain't gonna work, either.
Just had a talk with said middle kid and he insists that he is backing up his iPhone/iPad to his computer and has all his music and apps already there. But my iTunes still lists his iPhone/iPad and wants to update his iOS system from 5.1.1 to 6.1.  With his permission, I erased his iPhone backup from iTunes on my computer, but his iPhone still appears in the sidebar.
So how do I simply "de-list" his "de-vices" from my iTunes?
Love to figure this out now, as there is a daughter with an iPhone also in my iTunes who will be getting a Mac in the next year or so. (Her music/music video/iOS app collection probably makes up a good half of the iTunes library at the moment!)