How do I share apps with my kids in Android 10?

I upgraded the family tablet from a HUDL2 to a Teclast P20HD. In the HUDL (Android 4.4.2) when I bought/installed new apps I was given the option to share them with other (restricted) users on the tablet. When I clicked on the user in the user settings, I got a list of installed apps that could be enabled/disabled for each user (my kids). This system was simple and effective. With the Teclast (Android 10) I only have the option to add and delete users. No app control whatsoever. I setup a Google account for my youngest (5yo) which I can manage through family Link (as I do with my older child's devices) but then there is no way to share apps from my own Google account to his (the family library feature is only for teenagers and won't cover the apps I've already purchased anyway). I have purchased dozens of kids apps over the last couple of years and I obviously want these available in my son's account. I tried sharing apps with the Family Link feature inside the play store app on my account, but of the 100+ apps I've purchased, only 19 got shared. I tried adding a second Google account from inside my son's tablet user space (my own Google account, so I could get the apps again on the play store with my credentials), but it won't let me; expecting all further accounts inside that user to be my kid's school accounts and such. So I'm stuck. Is it possible to get the kids apps I have purchased into my son's user space on this tablet? If not, is it possible with some other tablet (I could send this one back and get something different) or is the KitKat way of things now deprecated and I'm stuck with having to re-purchase hundreds of pounds of kids apps?