Firstly, Dec is the great Christmas sale season, so you could purchase very cheap goods both for kids and adult. Just visit some large deparment stores, such as Harbour City and SoGo, you will purchase all. As for the light clothes, do you mean long-sleeved shirt and sweater? If so, you could find them everywhere.

In Hong Kong, there is a sale season from Nov. tp Dec. I think you might catch it. For cheap clothes, you can go to Ladies Market and Cheung Sha Wan Road. For some branded clothes in lower prices, you can go to Citygate Outlets at Tung Chung. The place for local food is definitely Temple Street Night Bazzar.

Thank you very much Sisley and HOngKOngman. What will be the weather temperature in mid Dec? Will it be very cold? What is appropriate wear to keep my 5yo kid warm? Is L'Hotel Nina very far from the places you recommended?