The knowledge base article
Set up Apple Watch for a family member – Apple Support (UK)
says
"The following features and apps are NOT available:
Medications, respiratory rate, irregular heart rhythm notifications, ECG, Cycle Tracking, Sleep, Wrist Temperature, Blood Oxygen, Audiobooks, Remote, News, Home and Shortcuts."
And nothing about Family Setup is mentioned in
Use Fall Detection with Apple Watch – Apple Support (UK)
and as it has to be a Watch with Cellular + gps it looks highly likely it will work. He could certainly call out to anyone.
It will not automatically call emergency unless it is a particularly heavy fall followed by a period of stillness so you will need to teach him to press and hold the side button and tap the SOS button if he is on the floor or feeling ill but conscious and moving his hand. Also how to use Phone app.
To be sure contact Apple Support.
Click here > Contact - Official Apple Support
or phone numbers
Click here > Contact Apple for support and service - Apple Support