Double or single entry Visa?

Hi,
We are a Danish family living in Germany, travelling to Australia via Hong Kong.

On our way to Australia, we will get off the plane and visit family in Zhuhai, China and as well visit Hong Kong city itself for a single day. We will then continue to Australia.

On our return leg from Australia, we will fly back to Europe via Hong Kong. We will stay in Transit at the Hong Kong airport itself and not come back to China or Hong Kong before boarding the plane towards Dubai.

Does the example above require a single- or double-entry visa?

Thanks for clarifying.
Jorgen Bruun