Imho even child can buy a Bitcoin, after localbitcoins was opened. Poloniex and other exchanges are also good places to buy Bitcoin or (probably) any cryptocurrency.
He can surely do the tasks but is he allowed? In localbitcoins, you have to meetup with the seller. Pretty sure the parent wouldn't risk his kid meeting up with a stranger. Plus, the seller will laugh at him if they successfully met up. There are other exchanges that lets you buy bitcoins but all of them can only be paid by using your bank account. A kid doesn't have a bank account. He would have to use his parent's.
He can perform all the tasks (e.g. go to the park and meetup with the seller, enter the debit/credit card details) but he simply can't because of his age.