His wife will be working in Hong Kong so she will have the Visa and any paperwork for Hong Kong.
He will be working in China and has the Visa and paperwork for China.
Obviously, most things in Hong Kong will be done under his wife's name just for simplicity as she will have HKID card, but for him, it will just be like taking a short holiday to HK every night and weekend. He won't actually be residing in HK (his wife and kids will be, and he will just be staying at their flat).