Nov. 21--Since you'll arrive at 6PM, I suggest you just do some walking around and then have a good rest in the hotel
22--In the morning, walk around 300 meters to Tsim Sha Tsui MTR Station, take MTR Tswen Wan Line to Lai King and change to Tung Chung Line, at last change to Disney Resort Line at Sunny Bay Station.You can stay there until the firework show. Single journey costs around HKD18.5 per adult and kids cost half.
23--In the morning, walk to Tsim Sha Tsui Station and then take MTR Tswen Wan Line to Admiralty Station, after arriving, take Bus629 to Ocean Park, Costs around HKD20 per adult. Kid under 12 yrs old and elders more than 65 yesar old can enjoy half price. After visiting Ocean Park, take Bus 629 back to Admiralty and then take Bus 15 to the Peak, costs around HKD20 per adult, and kids and elders still have discount.
24--In the morning, take MTR to Tung Chung Station, after arriving, you can either take Ngong Ping 360 Cable car or Bus 23 to Ngong Ping. The cable car has different kinds of tickets, you can go to the official website and pick the one you want. If take Bus 23, it costs HKD17-27 per adult, kids cost half.

At that time you can bring your kid a warm jacket, since in Hong Kong, the weather would not be very cold but you'll go to attractions just in case of the wind.