I’ve been to HI several times. One of the biggest wastes of time for me has been eating. If you try to eat 3 meals a day at a restaurant, you’ll not only spend a lot of money, you’ll just feel like you don’t have time to do stuff. I recommend 2 large(ish) meals, one in the morning and then one more for early dinner, like 4 pm. This means you also don’t have to rush any daily activity, and you have plenty of time for an evening one too. Plus you’re staggering your time in the restaurant away from the rush.
You’ve already got your luau scheduled, that’s good. Also, plan to have one (or two) flex day(s) where you don’t schedule anything at all before you get there. Then you can either change plans or pick up something you didn’t know about before you got there, or you can just have a relaxing day.
Plan to spend a half a day or a full day away from the wife. Don’t feel obligated to do everything together. Sure, it’s a vacation, but maybe she wants to go shopping and you just want a nap for a few hours. Or you want to hike this dope-ass trail, and she wants to meet a new friend for mai tais at the hotel bar. Feel free to take time apart.
Like others have said, swimming (floating) with (near) dolphins is overrated. (Ours sounds more interactive than DP’s, we at least had opportunities for the dolphin to swim and pull us along or push us out of the water with snout [Superman Pose].) Helicopter rides are actually cool, though. I may still have the VHS tape from when we took one while on honeymoon. Probably much more worth your time and money than the other.
You can’t have enough sunscreen. Far better to come back without a tan than to be a lobstrosity ruining your experience for half the trip or more.
If you’re only going to be there for 6-7 days, don’t try to get to 2 islands. I think 8 days is the minimum for 2 islands, because it really is a full day to go from island to island with checking out (packing, trip to airport, etc.), travel, and settling in again. If you’re going to be there 8 or more days, also seriously consider breaking it up into 2 relatively equal stays on 2 islands. We once did a 9 day trip with 2 on Oahu to start and 7 on Kauai, which was not enough and too much, respectively. (Kauai bored us after 5 days. And someone was sunburned.)
Do a sunset dinner cruise. It’s pricier than restaurant dinner, and it’s worth it. If you can get one of the smaller boats (<20 people) it’ll be more intimate and less “touristy”.
When you take pictures with your phones, you always say that you’re going to print them out but you never do, do you? Buy some disposable cameras and use those to take your pictures. That way you’ll be forced to develop them when you get back. Don’t take pictures of your food.
Wear your sunglasses when you’re at the beach. Learn how to ogle the ladies out of the side of your eye, so your wife doesn’t catch you looking. (Well, let her catch you looking once or twice, but not at the neck breakers, so you can be noted for the rest of the time for how good you’re being.)
Don’t buy the timeshare.