I am a Citizen of Sri Lanka and Permanent Resident of Hong Kong. I am currently out of Hong.

I am planning to visit Hong Kong with my Family, i.e. my wife and 2 daughters (all Citizens of Sri Lanka and Permanent Residents of Hong Kong) and my son (11 yrs) (Citizen of Sri Lanka with Hong Kong Dependent Visa only).
I assume my wife and 2 daughters and I can use the Hong Kong Permanent ID and enter Macau without entry permit .
Please let me know whether I could apply for a Macau VISA for my 11 yr old son while in Hong Kong and where I should apply (which office).