One I recommend is Hongkong Disneyland. This is only where you can go to a Disneyland located here in Asia. You can see here Tomorrowland, Adventureland, Fantasyland, and Main Street, the four main attraction. You can feel the magic this Christmas in Hongkong Disneyland.
You can visit too the Ocean Park. Your kids will really like the place and the ambience inside. It will be a lot of fun for a family vacation.
The third place I recommend is the Hongkong Musuem of Art. Its large collection gives you a chance to see over 14,000 items in history. It is open from 10:00am to 6:00pm only except Thursday.
Actually, there are over 20+ must-see places in Hongkong this Christmas. You can try to climb 431 steps to see 12,800 statues of Buddha at the Temple of 10,000 Buddha’s.
If you are with your girlfriend/boyfriend, then try to see The Star Ferry. You can enjoy a romantic date there.
Well, in any situation, it is up to you on how you enjoy the Christmas vacation. The places are just there as your setup in enjoying your vacation/visit.