It's complete, lunatic, totally unprofessional stupidity to let a child on the R/T.
Pretty stupid as it turns out because its going to cost him his job but the kid didn't seem to be having much trouble getting the words out did he? I can't see how safety was compromised, the pilots sounded like they knew exactly what was going on and the dad could have jumped in at any point.
As someone else has said it is quite interesting that the only people who don't seem to have a problem are the pilots (at JFK and on this board). Why I wonder, are we all too laid back or do we just not understand? Does it actually matter in what form the clearance was issued if you know it's authentic? If we were still using lights and verey (very?) pistols to issue take-off clearances would it be a problem if the kid had been allowed to switch on the light or pull the trigger?
It's the reaction that lunatic.