A Yoto player might work. They're designed for children. They have two knobs (with momentary switch) to control everything (and a small on/off button). They're designed to be usable by children who cannot read, primarily through Yoto cards.
These are just NFC type cards with with some kind of DRM. They allow your player to connect to an API, download the audio content (books, music) and store it locally for instant playback whenever the card is inserted.
Normally I hate vendor lock in stuff like this. But surprisingly they also sell "blank" cards. Using the app you can load any audio content "onto" them (same deal - audio is sent to cloud so it can be redownloaded if local storage runs out). These are pretty cheap and can be "wiped" and reused as many times as you want and you can write on them or mark them up. You can even design a specific image to show on screen when your custom card is inserted.
The hardware is good quality too and can survive daily life.
These are just NFC type cards with with some kind of DRM. They allow your player to connect to an API, download the audio content (books, music) and store it locally for instant playback whenever the card is inserted.
Normally I hate vendor lock in stuff like this. But surprisingly they also sell "blank" cards. Using the app you can load any audio content "onto" them (same deal - audio is sent to cloud so it can be redownloaded if local storage runs out). These are pretty cheap and can be "wiped" and reused as many times as you want and you can write on them or mark them up. You can even design a specific image to show on screen when your custom card is inserted.
The hardware is good quality too and can survive daily life.
https://yotoplay.com/