Travelling with a Minor.

Im a nanny and from Philippines. Im going on a holiday this Dec. to HK and Philippines and I'm bringing with me the 14 yrs old son of my boss. I already have a affidavit of support and consent from my boss and its already notarized from the Phil. Embassy here in Nairobi. What document do I need to enter HK with a minor? I cant find any information on their website. Do I need to apply visa for him ( He's a Belgian national)? Can I use the same affidavit that notarized by the Phil.Embassy to enter HK? Thank You.