Hi Alvyn,
One point I would like to clarify to you. Having a HK permanent residenship/HK born Chinese/HK permanent ID card holder doens't means that you have the Chinese citizenship(if you are talking about the Mainland China citizenship)
Of course being a HK born Chinese you enjoy the right to work and live in China, but to get the citizenship there are some criteria you have to fulfill. Please check with immigartion for your baby eligibility for HK residenship.
Back to giving birth in HK. Are you palnning to use private or government system ?
If you are using private, it will be very easy, just ask your OB to give you a referral letter with all your wife medical history and choose a OB in HK after you get back. He/she will make the arrangment for you. Any idea how far along will your wife when you come back ? If it is very late at the pregnancy, you may want to talk to the HK OB before you come back so he can make the arrangment for you in advance.
For government system it seems to be more complicated, you have to register with them beforhand or go in as an emergency case. There are many threads on this forum about giving birth in a govt. hospital. You may want to check.
Good Luck.