A family of 3 with a child at 4 yers old will visit Hong Kong

The taxi fee is around 250 HK$. The red color taxi should be taken and about 40 minutes need to be cost.
The airport express cannot take you to the airport directly, so you need to reach Kowloon Station in about 25 minutes and then take a taxi to reach your hotel. The airport express ticket fare for a adult is 90 HK$ and child can get a 50% off discount.
Actually, it is suggested to take bus A 21 to reach Middle Road and then you can see the Mansion after you get off the bus. The ticket fare is around 33 HK$ for adult and child get a discount.
It is suggested to buy standard Octopus Card. If you want to take taxi, the tourist pass cannot be used. If you use Octopus Card, you can get a discount when paying.