MomBoard: E-ink display for a parent with amnesia

As a side note on his mother remembering that the tablet exists, it sounds like she has amnesia quite like Henry Molaison, a famous case study in neuropathology. He had very specific brain damage that seemingly stopped him forming new memories in the same way as OP's mother, but studies showed that he could remember some things, just not consciously. So for example he would have warm feelings towards people who'd been caring for him despite not remembering them, and would also pick up card games more and more quickly as he played them repeatedly despite saying he didn't remember the game. OP's mother remembering the tablet sounds very similar, particularly when paired with the feeling of being remembered and loved by her children.

This reminds me of muscle memory. I can play pieces on the piano even though I don't actively remember the sheet music of them. My hands just "know" what to do. Funnily enough the moment I start actively thinking about certain passages that ability worsens by a lot.