Visa Exemption, for one night stay in the city, when transiting through Shanghai airport?

My wife and I and our two adult sons will be travelling from London to Vietnam via Shanghai.

On our outbound journey we will simply transit through Shanghai airport without leaving it.

However on our return trip from Vietnam via Shanghai we would like to travel into Shanghai and spend one night at an hotel, and then return to Shanghai airport the next morning for our flight back to London.

Are we exempt for this excursion out of the airport in Shanghai. And if so how do go about getting the exemption ?

Thanks