For the Mrs Temple Street night markets are a must & Kowloon in general has everything to keep most shoppers happy. The subway system in Hong Kong is fantastic so getting around is easy. Get yourselves an Octopus card at the airport, you use it to pay for public transport except taxi's. Its amazing how far 100 HKD will take you. If you are staying on Hong Kong Island then the ferry to Kowloon across the harbour is pretty cool especially at night.
If you are feeling a bit adventurous & want to duck over to China for a bit of shopping you can get the train to Lo Wu/Luohu border crossing & go to Shenzen. If you have an Aussie or NZ passport you can get a 5 day visa at the border for about 170.00 RMB. ($30.00 AU) The train takes about 45 mins from Kowloon (Tsim Sha Tsui station) to the border at Lo Wu. You get off the train & do the border crossing. If you decide to do it during the week is best. It can get a bit hectic on the weekend. It is worth doing & the change in things from HK to China is an eye opener.
Partying is good & there are bars everywhere. I liked the area on HK island near all the Ferrari & Lambo dealers. It seemed to be a bit of an expat area & was pretty wild. Cant remember the name of any of the places though.
Dont be afraid to explore either, some of the best stuff I have found in HK & more so China is ducking down alleyways off the main shopping strips, it is amazing what you can find. Dodgy little alleys can open up into a whole new world.