Even though this is one incidence at least   when other parents read this  it will make them aware of this and question other areas of the home that could be hazordous WELL DONE. It may be a small piece of advice but  big in so many ways it will definately go along way to help other people be aware and on guard.

What a smart little boy you have lucky he was there, he has good skills in an emergency for someone so young.

There are many so-called 'hidden dangers' around the home & this is one of them... Perhaps you could expand, (as Rhukia suggested) on the topic and mention some of the other dangers that every day objects present in the home.  Thank goodness your son had the presence of mind to come & get help for your friend's little girl & a tragedy was averted; you should be proud of him.

While it is a fantastic reminder to parents about the "unnoticed" dangers, perhaps you could extend on your advice about how to do a risk assessment of your home - the best tip I was ever given, was to crawl around on my hands and knees, take a look from their veiw and you'll be amazed at the things you'll discover. Then perhaps extend further about how to minimise these risks, ie don't have beds under windows, use furniture to cover electrical sockets and so forth, and if a risk can't be minimised or removed suggestions on preventing your child coming into contact with it or when old enough explaining the dangers and so forth. Good try tho'. :)