If you want to take airport express, you can get off at Kowloon Station then change to free hotel shuttle bus K3 to the hotel. Airport Express costs 90HKD per person, about 20 minutes or so. The hotel also has shuttle bus service at the airport, 120HKD per person. If you have many places to visit during the three days, you can consider to buy a kind of Octopus costing 300HKD covering airport express to and back from the city center and free metro ways without limitation within the three days. If you do not take airport express train but metro (need transfers but cheap), you need not to buy the card for only three days.