@QFY-You are judging the boy and his parents for their decision to allow him to compete.
First of all, while practicing law might seem that way in John Grisham novels or “Law & Order,” it doesn’t exactly work that way. Further, how is it not competing? Each side wants to achieve a different objective. That by definition is competition. It’s the same in business and just about every profession.
So you’re bringing me a Shar Hatziyon which apparently doesn’t even exist according to Sam2, that doesn’t assur anything or even apply to the situation as a basis for condemning the kid’s actions. I’m glad you are such a givaldike posek that you can equate recommending not singing to a baby, (not assuring it), to assuring singing for a parnassah.