December My 19 yr old and 12 year old kids, my cousin and I were visiting Hong Kong, first time.

1. From HKIA to your hotel, I suggest you take airport shuttle bus no. A21 and get off at Middle Road, Nathan Road. After getting off, you can easily walk to Chungking Mansion.
2. Transportation and suggestions for your travel plan:
Day 1: You can experience the Big Bus Tour for one day’s sightseeing. It is more economical and convenient. It has Island Tours, Kowloon Tours and Stanley Tours.
Day 2: Walk from your hotel to Tsim Sha Tsui MTR station to take Tsuen Wan line to Lai King, where transfer to Tung Chung line and get off at Sunny Bay. After that, transfer to Disneyland Resort line to the Disneyland. You can use the same way to return to your hotel.
Day 3: Still take Tsuen Wan line to Lai King and transfer to Tung Chung line to Tung Chung station. After that, take cable car to NP360 to see the Buddha. If you plan to travel in Macau, you can take a ferry at China Ferry Terminal, which is even within walking distance from your hotel.
Day 4: Except for taking a taxi, you can take overnight bus no. N21 from Tsim Sha Tsui to HKIA in around 80min. This bus is in service from 01:30 to 05:10 every 20min. You can catch that to catch your early flight.
May help!