We will be in hong kong on sept. 5 to 7, 2015 with our 4 year old daughter.

According to the weather forecast, it will be a bit hot. The average temp is about 85F. And there are light showers in 5th and 6th, but they will only last for few hours. 7th is sunny the whole day.
Just bring some rain gear if necessary, and dress your kids with T-shirts and shorts.