Years ago the parents of one set of second cousins of mine went out to the cinema one evening, leaving 17yr old boy in charge, 14 yr old girl and younger brother.
Phone rang, 14 yr old girl got off sofa to answer it and dropped down dead.
Yes undetected heart defect.
People are going to die at the most inconvenient times and in the most inconvenient places for OTHER people.
It's not about other people.
Just talk honestly and sensitively to children about the subject and get on with being active and as happy as possible in a fairly futile existence. 
Edited: 01/10/2012 at 18:27