I agree with another reader that an Amazon Echo Show with "Drop In" will auto-answer a video call for him.
The easiest way to set this up for him is to add it to your Alexa (Amazon) account and then just change it to his Wi-Fi. There are concerns that he could say commands to it that might affect your account, so be sure to turn off "Voice Purchasing".
If you instead want to set up an Amazon account for him, you will need to have a separate "mobile number" for him that is used as a reference number by Amazon. If you want some detailed setup instructions, do a Google search for this article:
"How to Set Up Alexa Calling For a Loved One" on Tech-enhanced Life
