Parental controls, tablets, and dyslexia

Hi All,

My 9 year old son was recently diagnosed with dyslexia. We have a Learning Ally membership because he can listen to many of the supplemental history books that he loves, but that I would never have the time to get through. We have a kindle fire so that he could listen to audiobooks, but he cannot access Learning Ally or any other dyslexia apps with the Kindle Fire. Right now, I use my phone to turn on the Learning Ally book and then let him have it. I am not at all comfortable with this, because I know he could explore all kinds of content when I am not present, through my phone and also through the app.

I am quite concerned that I have to have any device unlocked to allow my son to see the words being read on the screen. I try to keep physical copies of the books, but it is helpful to have access to the screen to see which page or section is highlighted.

Does anyone have a positive experience with a particular app and a particular tablet that would allow extremely limited access to the reading apps and the content within them?