There is a very nice wreck dive just off the harbor entrance in Willemstad. It is the Superior Producer, which sits upright in 32 (105 feet) meters of water.
Vaersenbaai is on of my favorites. It is a location where they used to dump old cars. There are about 50 to 60 vintage cars, a barge, and a tugboat between 25 meters and 57 meters. (80 feet to 190 feet) the tugboat lies on its side at 57 metes, but is easily visible from 40 meters (130 feet)
The coral at all of the dive sites is incredible, as are some of the wall dives. You will almost certainly see 6 foot green moray eels, barracuda, Spanish lobster, rainbow parrotfish etc, etc.
As far as other things happening on the island, there is plenty. It depends on what kink of a scene you are looking for. There are live bands plying at some of the beaches with dancing until dawn. Numerous clubs and casinos, or just relax with a few drinks on one of the amazing beaches. The water temps are 30 30 C on the surface and 28 29 at 100 feet. We are in the rainy season right now, so expect to have a few rain showers. It typically showers for about 15 to 20 minutes in the morning a couple of times a week. Air temps these days are about 31 33 C in the day and down to about 25 26 at night. Not sure what that converts to in F.
Here are a few links for you to have a look at.
www.kikotakiko.com
http://curacao.pagina.nl/
http://www.cura.net/weather/
http://www.ten-ham.com/Files/htm.files/cur.sites.htm