I posted in another thread, but i am starting a new thread to get more traffic. We will be there in late April of 2020, 7-8 days on Oahu and a day or two on Maui.

Can you give me pros and cons for hotels/resorts in the following areas?
Waikiki (other than the obvious)
Kahala beach
Ko Olina lagoon resorts, specifically the Marriott.
North Shore, specifically Turtle Bay resort.
Other?

Referral for a good Pearl Harbor tour.

Whale watching suggestions.

Referral for half day fishing charter.

Referral for snorkeling

Which inter-island airline for island hoping or other transportation?

My wife wants to do a real luau. Is it possible to get an authentic experience?

Waikiki
Cons: Crowded, more expensive, smells of coconut suntan lotion
Pros: You're in the middle of it all

Kahala beach
Cons: Expensive, but not as bad as Waikiki
Pros: Still in town, but a bit out of the way, you're near a golf course (if you're into that sort of thing).  You're near a mall

Ko Olina lagoon resorts, specifically the Marriott.
Cons: Expensive. One way in, one way out, you need to plan a head if you want to travel, traffic out there can really suck
Pros: You're away from town, nice if you want to get away, lots of amenities.  Head west and you're in Waianae (this could be a con)

North Shore, specifically Turtle Bay resort.
Cons: Expensive, you see a pattern yet? It's a bit of a drive, but hard to get lost, again the one road thing depending on route  Since you're going to be here in the winter  you'll be here for the big surf, traffic, one road, keep that in mind
Pros: You're away from town, near the North shore proper.  Haleiwa is a nice town, part local part tourist trap, fun times!

Referral for a good Pearl Harbor tour.
Whale watching suggestions.
Talk to the hotel, in advance if possible, they can get you a good rate or point you in the right direction

Referral for half day fishing charter.
The best deals I've found was through googling.  Your hotel may be able to hook you up with a group charter.  Again, good to ask.

Referral for snorkeling
Hanauma bay, if you opt for the last two you're in for some driving

Which inter-island airline for island hoping or other transportation?
Hawaiian, maybe Mokulele

My wife wants to do a real luau. Is it possible to get an authentic experience?

Sorry can't help here, our definitions of luau probably differ greatly.  Although I heard Germains is still ranks highly.

other
You might want to check out the Polynesian Cultural Center https://www.polynesia.com/

How much time should we need on Maui? I would rather fly over and back in one day. Will that be enough?

Sorry for the late replies, I don't check back often.  A couple of days should do, it all depends on what you want to do.

We will be at Waikiki the second half of April for 7 nights. We chose Waikiki because my wife felt that we will probably only get to go to Hi once so she wants to see as much as she can on Oahu. Also, Waikiki has access to tours, shuttles and such.

One question about fishing. My wife hears that the seas are rough around the islands.

How rough?

Is deep sea fishing in HI pleasant? I could probably handle a little surf, but i doubt my wife would be happy if she is tossed around.

It depends, what island, what time of day and the weather
Off Lahaina in the morning the ocean is pretty calm, in the afternoon when the wind picks up it can get a bit choppy
And the ocean can be effected by storms hundred of mile away causing high surf

If you want excellent offshore fishing in consistentlypleasant conditions, Kona is the place.  None of the other islands come close.  With the cheap interisland airfares it is worth it to fly over from Maui or Oahu.