Thank you! That also confirms what my son had concluded from his research. That my own citizenship claim seems solid, but I probably can't pass it along to him. But we figure it probably couldn't hurt. And it would certainly make travel and extended visits easier.
Meanwhile, I got some unexpected help with the second part of my question, how to handle my father's birth certificate. At my son's suggestion, I contacted the Canadian Consulate here in SF.
I thought it was a long shot, because their website makes it clear that they do not address questions around immigration and citizenship applications. Their mission is to help Canadians, after all. But my son suggested it was worth a try, since I could argue that I was, in fact, a Canadian. That struck me like begging the question! But it was easy enough to e-mail-them and ask if they had advice about how/if I should get a copy of that old birth record, and if by chance they could help.
I heard back within the hour! Yes, they are able to copy and certify documents like my father's old birth certificate and their "soft seal" is attached to the copy. The cost is modest. Wednesdays, 9-12 only. I just have to make an appointment. So that part of the problem is solved!
Are Canadian officials always this nice?
Perhaps it helped that I explained why I was seeking a citizenship certificate at this late stage in my life: For the family reasons I explained above, and not simply as a reaction to the current political shift in the US. (Although that did play a role in the young couple's decision about where to settle.)
Wish me luck!