Disneyland: take tsuen wan line from TST to Lai king, change to tung chung line to sunny bay, finally change to disneyland resort line.
Ocean park: take tsuen wan line from TST to Admiralty to take bus no. 629.
I think you can take bus No. A21 from HKIA to Middle Road, and then walk for about 2 minutes to Miradoe mansion.

Thank you for the response. How much it may cost when riding a bus No.A21 from the HKIA? Then how much it may cost when riding a MTR from the Tsuen Wan line to the disneyland resort line? What is an octopus card? I'll be staying in Hongkong with my sister and my kids .

fOR oCEAN Park, the MTR is just infront of the Mirador mansion. Take the MTR Red Line going to Admiralty. Then Exit at Exit B... On Road Level, you will see a booth selling Bus Tickets to Ocean Park and Ocean Park Ticket. The Bus awaits you to the Park. I suggest you buy a return bus ticket so that you will not queue going home.

For Disneyland, take the MTR again just infront of your Hostel.. Buy the MTR ticket to disneyland. There is no straight subway to disneyland. You have to transfer to another train in either Lai King or Tsing Hi Station where you go to Sunnyvale station. From Sunnyvale, the disney train awaits you. Do not worry, just follow the flow as most of the tourists go to disneyland.

Once you exit to the Immigration, walk forward to the huge Main Lobby of the airport. All are going there so no problem about that. Once in the Lobby, turn to the right direction leading outside where you see buses lining up. Take Bus A21. (Signs are very evident). Just hop in with your luggages. There is enough space for luggages. Pay 33 hk dollars each upon getting in the bus. So i suggest you have exact hk dollars since they don't accept us dollars or no change at all. The trip is about 45 minutes to one hour depending on the traffic. Get off at Middle Road Station. In the bus, an electronic sign is flashed so you know which station is next. Upon reaching Middle Road station, walk backwards around 50 meters, again backward.. and you will see Mirador Mansion. You also pass Chungking mansion. A little advise, be careful on those trying to pretend to help you. Just look into the signs of the hostel and the floor where it is located, and go straight to them. You might fall into this trap. Enjoy your trip.