For 12 days? I'd probably go see other islands. Few good places to see in Honolulu for sure... but rent a car.
Stay a night or two in the waikiki area (very touristy), soak up the beach...
Surfing there isn't anything you see on tv, it's very very gentle... it's essentially going on the smallest dinkiest waves you can find but very fun but tiring.
But as for the MUST DO's:
1) Pearl Harbor - Can't go to hawaii and not see this...
2) Some battleship you can go on but I can't remember the name. Was pretty sweet, but my sisters thought it was pretty boring.
3) Many beaches all around here
4) Golfing here is stunning, but very expensive
5) Rent a car, and drive around... very beautiful place with lots of trees and beaches. There is a basson(sp?) where you can do some whale watching and snorkle in shallow water with LOTS of fishes. Was pretty sweet, even my grandma went in for a bit and she's terrified of swimming.
What not to do??
There was this meze... ruins (can't remember the name) but it's essentially a mini-disney world without the rides. So they just have shows and dinner. Very expensive... and not worth it AT ALL (IMO)
2) Spend your whole time in Waikiki/Honolulu
- Diversify your time and visit other islands. Waikiki gets dry after a few nights, and Honolulu is about worth a weeks stay. Go to Mauii or some other islands but I didn't stay there for very long so I wouldn't be able to tell you much.
Have a good trip!
