Split my review into two:
Honestly as an adult that spent most of my trip snorkeling the reefs this was not the most entertaining experience. I am unable to scuba anymore for health reasons so it was cool to get lower and see some wreaks but it's not a LOT different than a simple snorkel if your ok diving down. The kids seemed to love it. My fiance is the reason we took the sub and he was amoung the excited kids because he'd never been in a sub (I have... so it's not as novel)
The luau is entertaining for sure and you will need to see one from some location. I choose island breeze because of the vegetarian dish they offer in addition to the buffet. The pasta dish I got was alright but not special but with that along with some menu items I was fairly satisfied. Most traditional hawaii food is not vegetarian, so from that perspective it's not a buffet of cool things for a veggie but it is for a meat lover. They do lift the pig out of the pit at this one (I guess not all do). Drink are alcoholic but don't taste good.
There is another tier of seating at the luau that allow you to get vip access, more entertainment and the best seats. Buying from viator will not get you this access or allow for an upgrade - you'll have to buy your luau elsewhere or some the hotel or something. I'm not sure the cost of that, but I would have liked to have better seats as we were way in the back corner and that made it hard to see the dancing or get any pictures.
Atlantis sub trip was very good, saw some amazing coral reef fish and dived over 2 wrecks which was very spooky! Also visitted the fish nursery where locals are trying to restock some of the more beautiful of the reef fish - Yellow Tang were everywhere! Very informative guide.
The Island Breeze Luau was also quite good. The food was excellent, but drinks expensive after your free Mohito. If its a cultural experience you're after, the Celebration of The Kings at the Fairmont Orchid is a much better and more exciting show. Overall, a good combi-tour.