reaching on 18th at hong kong airport to grand harbour hotel what's the best way?

You refer to the Harbour Grand Hotel, right? Well, it has two branches:
For Harbour Grand HK, you can take Airport Express (AE) to HK Station and transfer to free shuttle bus line H2 to your hotel.

For Harbour Grand Kowloon, take AE train and get off at Kowloon Station. Transfer to shuttle bus line K1 to reach exactly.

Thank you. Also i am there (2adult +2 children) for just 3 night covering ocean park- whole day , disney- whole day , and one day fro sightseeing in hong kong. Do you think its advisable to taken 3 days airport express travel pass (mtr).

regards