Apple ID and App Transfer

Just bought my 10yo his first phone. When we originally bought his iPad years ago, we didn't create a new Apple ID for him - we used mine. So his iPad has my Apple ID, and therefore my Apple ID has his 8 million game apps. (You should see my phone, it's littered with all of those games which drives me crazy.) I've been reading that he should really have his own Apple ID, and I'd like to go this route for him with the new phone. My question is - all those games that we've installed, purchased or free - when we give him this new phone, is it possible to get all those games and apps moved from my Apple ID to his new one? Did that even make sense? How do I undo the mistake of years ago when he didn't get his own Apple ID?

Thanks!