My family ( 5 adults) will travel to Hongkong on october for 3N/4D.

Upon arrive at Hong Kong Airport, you could take bus A21 and get off at Cameron Road, Nathan Road. Then, walk down along the Nathan Road for several minutes, you will find the Mirador Mansion on your left hand, where the USA Hostel is located. The bus fare is HKD33/adult.
The Novotel Citigate Hotel is located in Tung Chung, where you could get to by the Tung Chung Line of HK metro directly. From this hotel, you could take bus S1 to Hong Kong Airport at very reasonable expense.

As for the tour, it is suggested that you go to Victoria Peak on the first night. However, you may miss Madame Tussauds there. On the second day, you could take a ferry from Tsim Sha Tsui terminal to Macau, and return to Hong Kong in the afternoon, finally transfer to the Novotel Citigate Hotel. The third day should be spend in Disneyland. On the last day, you could go to take Ngong Ping 360 from Tung Chung and get to the Giant Buddha. When the tour ends, you could also do some shopping at CityGate Outlet just in Tung Chung, and finally depart to the airport. I'm afraid that you do not have time to the Ocean Park.
Ps: Due to the short time in Hong Kong, no need to purchase Octopus Card.