Comment by bapak
I placed a Facebook Portal at my 90-year-old grandma's and she video calls me with it. Extremely easy to use.
I fear the day Facebook finally kills it and I have to navigate the nightmare that are tablets, their ever-changing UIs, and endless unprompted prompts.
You could look into MDM solutions. These are meant for unattended devices like kiosks in public spaces. You should be able to control devices remotely and lock them down to only the essentials.