Well, here's another find by me just today... To the best of my knowledge this isn't mentioned anywhere either from my research. Correct me if I'm wrong, but I know of no child in GT5 other than this one I just found. This one is really hard to find, so I'll let you guys have your fun and do your own hunting to see. Here's some photos as a hint... Good Luck !
That most surely was an 'Easter egg' that belonged with Bond at Eiger. I see you've found a few other oddities, too, that could have been placed in the 'GT5 Easter Eggs thread' - wherever that must be buried now.
Until now I firmly believed (obviously dependent on the fallacy of insufficient evidence) that there was not a single person who bought their child to the races in GT5.