My baby is Australian and wife is Chinese. Currently in Shanghai!

Hi there,
My wife is Chinese and we have a 6 month of child, along with my mother in law, they are now living in Shanghai due to the wife having to finish her studies for 8 months. Mother in law will leave before 3 months. Can we apply for an extension of stay for our Australian baby? Meaning he will have to stay 7-8 months before wife and bub come back. Will there be a fine or a big fee? Would they be more leniant as he is still so young?
Thanks