iTunes 12 doesn't make a difference but
Find my friends and a clove of garlic do...😝
Magically works on an old iPad where I did a fresh reinstall after erasing and restarting with my very same iCloud settings
Didn't work at the beginning but after the magic installation of the Find my friends
it works. What I think is part of the problem is a second iTunes account shared on the same device
that complicates everything. If you have any app downloaded from one of your children with his account you are busted
This is what I figured it out.
1 Eliminating the apps not yours ,
2 erasing everything from the ipad after having done a good backup without the apps involved
3 and then restarting the iPad restoring the backup without the wrong apps, works.
4 Installing Find my friends( doesn't work if you just share your location and don't have the app)
5 After that it's possible to install the apps that were causing trouble before
and even stop sharing your location
Somehow the system is writing somewhere the blessing for your to share with your family or not
It would be nice to know where and why Find my friends works
But for sure these days you cannot rely on Apple for helping you: in my case they even gave me wrong informations like books are not sharable anymore when is not true..like someone said earlier it looks that we are becoming Microsoftizided 👿