Four or five years ago when I got my son a refurbished iPad to play with, he was too young for his own Apple ID, so I set it up with mine. Now he's old enough, he's got an iPhone with an Apple ID of his very own (with family sharing enabled), but his iPad is still set up under mine.
I'd like to swap "ownership" over to his Apple ID, but I'm not sure what will happen when I sign myself out of iCloud on his device and sign him in. Will it delete his apps, or his save game files? All the tutorials I've looked up say he'll "lose access" to anything purchased with my iTunes account. I have other iDevices with apps purchased via several different iTunes accounts and they all seem to co-exist happily as long as the correct password is entered when they need to be updated, but I've never swapped the iCloud account on those.
He doesn't have an Apple Music subscription or any purchased music or podcasts/books/movies. He is already signed into the iTunes store with his own AppleID, so some of the apps he has purchased himself already.