AFL player Nic Naitanui is the boy in question’s idol and he has said nothing about the outrage that has been fanned predictably by white social justice warriors who have taken offence on his behalf.
The point of a costume is for it to be recognisable. When you are an incredibly pale skinned little white boy if you want to look like your hero Nic Naitanui you need a wig and you need to change your skin colour. Racism is about making fun of someone or thinking less of them because of the colour of their skin. Dressing to emulate someone you admire can never be racism.
Even if at some point the boy’s hero decided to take offence that would not change the boy’s intention. I admire the mother for not telling her son that he couldn’t emulate the man he admired for fear that some white mothers somewhere might get their politically correct knickers in a twist.