i will be in honkong from 4th feb'18 to 19th feb'18 with family including 2 kids (3 yrs and 8 yrs),

Hey, there may be many cloudy days during that time, with the average temperature of around 15C. It can be a little cool. Light rain may happen sometimes, but won't last long. I suggest you wear light sweater, jacket and pants. In the early morning, long john may be needed.