You are grossly misunderstanding children and money, and in doing so unwittingly point out the flaws in capitalistic society.

The kid who ends up with the most tokens in this scenario will be the kid who does start selling candy for them. Because their parents will buy them candy, that they will then turn around for a profit. That, or the kid who threatens to beat up the kids who read in exchange for tokens. Or both. Regardless, the concentration of wealth in this token economy absent rules of control will not be the children who engage in the behavior you're trying to incentivize. You're already suggesting it with your system (re: the sharky kids)

The fundamental truth behind capitalism(remember, capitalism is the system that rewards ownership over labor. and is entirely unrelated to the exchange of goods on the market) is that everyone wants something for nothing and the moment you commoditize something, people will try to get it for as little effort as possible.

Here's the thing. You view money as a token not attached to real world value. That is absolutely not the case. The origins of money came about because a barter economy cannot scale. I can trade my services as a carpenter and build you a table in exchange for food you've grown on the farm, but if the farmer needs to buy new seeds, you can't turn around and saw the table in half as a fair price for their trade. Money is the agreed upon placeholder that stores value of labor or goods, and it's value only exists in transactions.

What your proposition suggests is no different from giving a child a dollar to read a book. It's still transactable money, and still a part of an existing economy. Making it crypto only means that their purchasing options are limited, like getting a piece of pizza, or winning skee-ball tickets at the arcade.