planning to be in HKG from 29th april to 4th may total 5 people. can u suggest best pass?

Well, Standard Octopus Card is suggested. With it, you can use on almost all public transportation in town, and can also enjoy some discounts. And the 50HKD is refundable and yes, you can retrieve it at the Customer Service Center of all MTR stations.

The metro leads to Disneyland directly, but is not available to the other two. To the ocean park, the bus way is to take bus no. 629 at Central or Admiralty, and to the Buddha, you'd better take the cable car near Tung Chung MTR station.