Yes, both of the T1 and T2 of HK Airport supply baggage storage. You could find the desk respectively at Level 5, Arrival Hall, T1 and Shop 001, Level 3, T2.

From the airport to the Big Buddhas: you could take the Bus S1 (3.5HK$)or a taxi in blue color (30HK$)at the Ground Transportation Center of HK Airport to reach the MTR's Tung Chung. Here, you could take the bus 23 to reach the foot of the Buddhas directly in one hour.

From the airport to the Hotel: you could take the Airport Express (90HK$/person) and get off at Kowloon. Then, please take the free shuttle bus K4 which could take you from Kowloon to the BP International Hotel directly.

If you will stay in HK over 3 days, you may consider purchasing an Octopus Card which will ease your trip. There are two kinds of Octopus Card for travelers. One is 220HK$ allows you to take the Airport Express for one time and unlimited rides on HK MTR in 3 days. The other one is 330HK$ allows two Airport Express single journeys and inlimited rides on HK MTR in 3 days. The 50HK$ deposite of both types will be refunded to you.

Thanks Mr Shan,

How much do they charge for the baggage storage at the airport?

Basically the only MTR we are taking is
1st day Hotel to Victoria Peak and back
3rd day Hotel to Victoria Peak and back
Airport express one way on first day

Is it still advisable to buy octopus card?

Well, if so, I think you don't have to rent an Airport Express Octopus Card~