Finding vacation activities in Hawaii isn't hard. Basically, your number one activity will be hanging out on the beach. There is more than one way to do this, however. Swimming can be fun, and sunbathing is a necessity, but you should consider some other Hawaiian activities while you're at it. For example, just renting or buying a snorkel and a pair of fins can make your beach trip much more exciting. There are so many things to look at under the water! When I was there, I saw sea turtles, coral, and literally dozens of species of tropical fish. The water was warm, the waves weren't too bad, and the views were out of this world!
Of course, no Hawaiian vacation is complete without at least a few tours. There are literally hundreds of activities in Hawaii to choose from, and it really depends which island you are on. I went on my catamaran tour around Kauai when I was visiting, and I loved it. I would recommend it. You see, on that particular island, a lot of the shore isn't accessible by foot. The mountains are too steep in the interior, so the gorgeous sandy beaches on the North of the island can only be seen from above. Not only were the beach is beautiful, but the majestic towering cliffs were absolutely awe-inspiring. My Hawaiian vacation trip definitely wouldn't have been complete without seeing it.
One of the most classic activities in Hawaii is the luau. If you are only going there for a week or two, give up the idea of seeing a traditional Hawaiian luau they are very hard to find, and generally closed off to tourists. That doesn't mean that you shouldn't go to see one, however. You will be able to enjoy delicious Kahlua pork, fire dancing, drinks, music, and good company. Add to this the scenic backdrop of the beach and the sound of the waves crashing over and over again as the warm tropical trade winds blow ceaselessly, and you're all set up for a heck of a good time.
In terms of nightlife, the scene varies greatly depending on which islands you are visiting. Kauai is actually pretty quite at night, but the big island is something else. There is a great music scene, as well as theater, movies, and anything else you might expect in a thriving community. All in all, there are more than enough activities in Hawaii to keep you busy!