Dr. D…
rather than spending the time retrieving and putting on the helmet from the back deck, I would have simply retreated to find a safer passage where rocks are not a problem, i.e. deeper water. I don’t even think I would flip in that situation. I just think it sucks to work my way around rocks in shallow water with a long boat. If I wanted to do that, I would be in my ww boat on a river instead. 
sing
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Yes. There’s no reason to not to wear a helmet. I always wear my helmet when paddle boarding on the lake. I have a really cool matte green Pro-tec helmet that I always wear and it’s important for safety.
Not unless they are paddling shallow water full of rocks.
This reminds of an odd contract I had once with the US Air Force. We were in the Nevada desert assessing the chaff and flare debris that falls out of jets doing training flights. We found fire scars, weather balloons, and some ordinance. Plenty of wild horses, desert tortoise and twisted sheet metal.
My supervisor insisted that my crew wear hard hats. “Okay boss.” We just left them in the truck.
For perspective, ACA’s insurance carrier does not require helmets for flatwater situations. And few entities are as risk averse as insurance carriers.
In my WW courses, if we have a long flatwater section I let students know that they can shed helmets if they desire. Few do unless it is a really hot, humid day.
No
Although, your now 30 year old daughters will be able to decide for themselves.