Aeroflot 593 was already mentioned but I'll re-mention it just in case. That was also an "innocent attempt to please a kid". Many people are dead.
It is amazing to me that on the one hand in threads parallel to this one there are highly technical discussions of minute details that may have caused one accident or another (and numerous deaths and injuries) and right here I see people defending captain that permits unauthorized untrained person to be at the controls of flying aircraft, no matter for how short of a time.
Would it be a fair game, then, to have someone's child who is very interested in medicine hold a scalpel or poke around inside while there is a patient being operated on? Would it even be ok to let same 15 y/o drive a car just a little bit on a busy highway? Didn't think so.