The St. Regis there is definitely worth the money. Awesome breakfast, cleanest place I have ever stayed, and the beach front is spectacular! The weather is supposed to be more sporadic in the North, but we stayed in the north and the south and had better weather up north so I think it is a crap shoot anyways.
Helicopter ride is a must, we did a solo one, but it was a little too long. About an hour is more than enough in my opinion. There are some group ones that land and go to the Jurassic Park spot, heard that is pretty cool. Both my wife and I almost got sick by the end of it because they are going in and out of the coast line.
Waterfalls and hikes are a real attraction obviously. If you're not into hiking you can drive to the top of the one mountain there and take pictures / walk around etc.
I didn't golf, but would love to try next time we go. Really, the trip goes so fast, just enjoy yourself and don't put too much on the schedule.
If you drive to the north towards princeville, there is this great road that almost reminds me of the road they show in the Masters commercials on CBS. There are a ton of areas that you can just pull over and check out sites. It really is the most beautiful place in the world.
Traffic is tough through the main areas, we did the sports car thing for a rental but could never really go over 50 anywhere haha. Sunscreen! I was so burnt laying out in the sun for like 2 hours.
Food:
Tidepools at the Hyatt is great. The crabcake (not a huge fan, but loved these ones) and the lava cake are well worth it.
Somebody there will probably recommend Beach House Restaurant, we found it kind of touristy / not really worth the price. Calamari was weird there. They do have people there to take your picture and what not, very nice looking place, but I wouldn't go back.
Ask a local what's their favorite spot, I can't remember the name but it was like a local pub that we went to that was great. It was near some local shops.
We did a luau, figured we had to while we were there. I think it was at the Hyatt?? It was good, pretty entertaining and met some people. Went on stage and danced with some people.
I had a local beer there, but can't remember what it was. Not bad though.
Have fun, super jealous!