Which card to buy for taking HK MTR

Hi there
We are a group of 5, 4 adults and 1 child staying in HK for 3 nights
We arrive on Wednesday 2nd July and depart around midnight on Saturday 5th
We would like to travel to and from the airport
We also plan to go to disneyland, the peak , Lantau island for the cable car rise and have a boat trip booked for the symphony of the lights leaving from north point east passenger ferry pier
We are staying the butterfly on morrsion at happy valley
Is the airport express the best card for us to buy and will it cover all the destinations and the whole of the time we are in HK
Thanks
Mel