Even though she made the purchases with his money and she should therefore require his consent, at the end of the day it is for the good of the market that a husband should honour his wife's debts. If he is over six years of age and understands the concept of buying and selling, they could be. However, since their concern was only that such a child who has to fend for himself would have some means of obtaining his basic needs, it does not apply to a minor who is cared for by his parents or a guardian. It therefore follows that a purchase made by minor who has a parent would not be valid. Furthermore, it would seem that he could also demand the return of the stolen money Shuki used to buy chocolate.
Parents commonly send their children to the grocery to buy food and other small household items.
The only reason why the shopkeeper is prepared to supply the goods via these children is because they trust that they have been sent by their parents, who will pay for the purchases. In order that parents can continue sending their children to shop, it is essential that they honour the children's debts. The takonas hashuk dictates that Shuki's father should pay up. MDbusiness illustrates general Halachic guidelines, only. If you have a question, please consult a Rabbi who is well-versed in these laws.