if he still wants to hunt and you try to force him to stop, you are going to have a man hate you for the rest of his life....
has a doctor found him incompetent ( They have set questions they can ask to determine his mental state and that is the bottom line) and does someone have his power of attorney...
if not, well
you should know him better then anyone else and how he will take it
and if it's a physical problem and his age, well we all have to go sometime and I think going while out hunting or fishing, is the way I want to go...
if you could get him to go on the hunt without the guns is a good idea, most camps I belonged to has 1 or 2 older guys who didn't hunt, would walk a bit and did the cooking around camp....that might be enough for him
but if he thinks he still want to hunt...it could be a battle...........you probably already know how he is going to take it...
just my thoughts on it
good luck