We are booked the Harbour Grand Kowloon Hotel - is there a free shuttle bus to/from hk airport express?

I'm afraid there is free shuttle bus taking you to your hotel directly. Here is my suggestion:
Take Express Train to Kowloon Station, where you can take bus no. K1 to Hung Hom Station. At the station, you will find the free shuttle buses that provided by your hotel. By that, you will reach conveniently then.