I'm not trying to stir up trouble here, but my family's feelings are a big part of the reason why I wear a helmet, so ....
Have you ever considered how your son would feel if you were killed in a cycling accident? I wear a helmet because I wouldn't want my family living with the thought that, "If only she'd worn a helmet, she might still be with us."
Honestly, no. It is not something I've ever considered. I used to do risky things for money and I didn't think about it then, either. I lost a parent as a young child (unhelpfully late diagnosis of a treatable terminal condition) and have not once dwelt on what might have been. I may sound callous, but it seems unhelpful to do so.
I imagine my son (and the rest of my family and friends) would be sad about it if I were splatted. In my experience, that's what the loss of a loved one does to humankind.
I am now middle aged and live a fairly tame life. Riding without a helmet (hardly a quantifiable risk) is about the naughtiest thing I do.
I know people who think as you do, some of our dearest friends among them. I do not think it wrong to do so, but I do not think like that. It is a curve whose limit is beyond the horizon. Once we start with
'if only', where do we stop?
"If only he hadn't been on a diet, he wouldn't have walked back to the newsagent to change the semi-skimmed for skimmed. Then he wouldn't have had to cross that road again and that car wouldn't have swerved into the bollard on his left, causing him to step back to eaxactly the place where that fridge, falling from an aircraft, landed on him and squashed him dead."
We aren't here for long. It must be nice while we are and it should be our clear wish to predecease our progeny.