We use a shared drive, that way we can put everything on it we want to share...movies, books, etc
This is how I control my Mother in law......
She is too naive and trusting to have unfettered internet access, so I have her Kindle registered as one of mine.
We then meet up regularly for lunch, I update her book(s) using either WiFi, or a personal hotspot... then disable it again
That works well for us.
Funny thing is that when it comes to seeing my content, she has become interested in CJ Sansum, Rory Clements and even Bernard Cornwell!
Only downside is that her choices really make a difference to the "Amazon recommends" lists