how to get from hk airport to causeway bay hotel? what is the cheapest transport?to ocean park and disneyland

Which exact hotel do you plan to go? As far as I know, there are many hotels in that area.
Generally speaking, you can take A11 to reach that area.
To Ocean Park, you can take the local metro Island Line to reach Admiralty and walk to reach Admiralty West to take bus 629 to reach the Ocean Park directly.
To reach Disneyland, you can also reach Admiralty and then change to Tsuen Wan Line to reach Sunny Bay where you can find Disneyland Resort Line.