The main island is Oahu, which has Honolulu and Waikiki is in Honolulu. Waikiki is OK as a beach but not really any good for catching a wave on a board or bodysurfing. On the upside you might see something like a green turtle there if you have a mask, but the water can be murky. Maybe the canal draining out somewhere does that. People seem to like it though. Some places hire those wooden lounges for an unreasonable sum of money.
The food maybe is OK by objective standards but nothing to write home about by international standards except I think they might have a Nobu restaurant somewhere there, but it is mostly tourist food along the main streets there. They try and give it some sort of island feel by putting pineapple into the salsa and offering rice with everything. Everybody is selling something there, and car parking could be a bit expensive because there is little street parking in Waikiki. One of the hotels will give you non valet for $25 midnight to midnight I think.
You could go see the parts outside of Honolulu. There is some snorkelling place about 10 miles away Hanauma Bay. Its $7.50 to swim there and sometimes the car park is full, plus you have to watch a movie on habitat protection for about 10 minutes before they let you in. You will see some reasonable fish there, some coral, maybe not really colourful sort of brown coloured brain coral but it is OK. You could surf on the north part of Oahu.
Maui is another popular place. It seems well catered for with hotels, but not as cramped in with everyone hustling. You won't have the same level of public transport as Honolulu on Maui. I get the impression that it is fairly expensive there, I think because it has the big name as a surfing place. Its name is well known so you pay perhaps more. You might have to go to Molokini which is offshore from there a kind of sunken volcano crater. I did not visit it but I suspect it would surpass Hanauma Bay. But you have to go offshore for it.
Alternatively there is Kauai and the Big island called Hawaii. The volcanoes are on Hawaii the island, so if you want those, you go there. You can visit from the others for the day or stay there. Kauai is where they filmed a lot of movies including Jurassic Park. It has an interesting canyon, Waimea canyon which resulted from weathering over millions of years. So if you like that kind of thing. Don't bother going to Po'ipu for snorkelling on Kauai because it is hardly worth the effort, unless I suppose you are desperate. Also, just an impression, but I don't think the locals are entirely friendly there to tourists, (the original locals).
Kauai could be fun if you don't like the tourist scene of Waikiki. One of the things however is that these islands have a lot of rocky beaches so it pays to make sure you don't get a beach which is basically a rock shelf. There is a hotel on Kauai called the Kauai Beachside Resort or some name, close to the airport there on big grounds. You can't swim there because it has like a big rocky shelf at the beach outside the hotel. Which is why it has plenty of pools. The food can be quite good at that hotel, especially the seafood buffet night, but it is just as well because that island is much more rural than Oahu. Hence its nickname the Garden island.
It would be advisable to get a car on any island you choose, but especially Maui or Kauai or Hawaii. There are a few other low density islands Lanai, Molokai etc, but I think Oahu, Maui, Kauai and Hawaii (the island) would be the main 4. It is about a half hour flight from say Oahu to Kauai, or in the other direction south to Maui, and some extra for Hawaii island. You need a 90 min checkin though, so even though the flight is short, the formalities could be tedious.
You could maybe take the full tourist treatment in Waikiki and then visit Hawaii island on a day trip, or split the trip into 2 if you need volcanoes you will need Hawaii island, which unfortunately I haven't visited. In any case on the biggest 3 islands most of the developed areas are on the eastern sides probably because of freshwater supplies for populations. It tends to rain on those sides. The other western sides are left relatively undeveloped so that could change your experience just by reason of the side of the island which you choose. On Kauai for example there are a lot of really steep cliffs which are pretty inaccessible. Camping etc is regulated with permits. If you want wave action many of the south eastern situated resort areas eg Honolulu, Lahaina on Maui, are pretty flat.
