With one week, I also recommend one island. I have been twice to the Hawaiian Islands, 14 years ago to Oahu and Maui and just last spring to Oahu and the Big Island of Hawaii. I have not been to Kauai, but have heard it was lovely.
You want nightlife, go to Oahu. There are many luaus and shows to go see. There is also Pearl Harbor and Diamond Head. You can snorkel at Hanuamana Bay (can't spell).
We stayed at the HHV last spring and thought it was a very nice hotel with lots of action of it's own. We stayed in the Ali Tower and would definitely return. We also loved the Hilton on the Big Island. Very large resort and the Big Island is unique.
I would do a little research, pick one island and go to one unless you can spread your trip out to 10 days +.
Also, the nightlife is on Oahu. I don't remember any nightlife on the others, but we also were always with kids. :)