Is Visa Free Transit Available for me and my family ?

I am travelling from London to Hong Kong with my family and staying for 5 days. I am then travelling to Shanghai and hope to stay for 3 days after which I will fly back to London. Can I stay freely in Shanghai as I am not sure the route HK - Shanghai - London qualifies for the free transit as HK and Shanghai are within the same country and therefore possibly falling foul of the three region rule. Can anyone help.