The lack of comprehensive health insurance for him is worrisome, and possibly problematic.
Buy insurance for him. I suspect the cost of that insurance will be less than you expect, coming from the USA. (Of course depends on whether he has some health problems etc).
Americans are constantly surprised that health care costs in Canada - even straight out of pocket - are cheap compared to USA. I have a host of stories about this. And as a result, insurance for visitors can be very reasonably priced (friends have said cheaper than what they pay in USA as residents with insurance from work).
Of course may not apply in all cases, you have to do your own research on this, but you really should not let health insurance be the blocking factor.
*Covid is special case - insurers may not want to cover - but some provinces have specifically said covid-related treatments will be covered regardless of insurance, because the public health risks of not treating people already in Canada is more important than cost recovery from indvidual patients. Canada is not the USA.
[Side note: I am not claiming Canadian system is perfect. As a Canadian citizen living abroad without Canadian health insurance, I once found I could not get a flu shot - free at the local pharmacy - at all; there was simply no mechanism for me to pay, at any price. Absurd, but again - Canada is not the USA.]