I wear my lid when I feel like it. Its more confortable on long high speed rides and practical in a city atmosphere where a low speed accident my happen.
The problem with lid statistics is the application of the event and assumption. You can say anything you want with statistics. Closed head injury deaths are the leader in low speed accidents on bikes. If a helmet was not used in any death they treat it as a helmet related, avoidable death. A death from the broken neck if a helmet is used would not be blamed on the use of the helmet.
In any event, its a free choice. My question is more broad. Why with little folks at home is he biking anyhow? Is it a poverty thing? Helmet or no helmet, a bike is way more dangerous than a car. Its all a choice. Its his choice. I am sure he knows helmets exist and why.