the son ran it, and writes on his Facebook page that his mum stuck by his side for the entire race. "And finally to my amazing Father who physically broke out of hospital and managed to drag himself to that 25 mile marker to support us on down the final stretch and cheer so loudly his voice could be heard 200meters away over the sounds of hundreds of people, you will forever be my hero."
So the children are either in on it, or have been fooled themselves.
I just told my DM all that has come out today and she was properly shocked and very disappointed having enjoyed and believed the book. She did say she had thought it odd that he managed the walk with that kind of illness (retired nurse) but had accepted that it must be true as it was in print :).