When this flight is a connecting flight, then you have already your boarding passes for the next flight, so why you should check inn again ?

I would go to the peak, - if you never seen hongkong at night from the peak - this would be a great chance (also nice retsaurants) - fantastic view and a lifetime expirience...

You can easily go with Airport Express to central station (24 minutes) and there grab the peak bus or a taxi to the peak station (5-10 Minutes)..