We've done several weeks in Oahu and Kauai. I've had to work at a few hospitals on Oahu and we first started going to Kauai when we honeymooned there in 2002. I tend to be someone who primarily does local things, so here are some perspectives you might not get. I won't cover Oahu, as I am probably going to overload you with Kauai detail here. Let's say I'm just as bad with Oahu details...
Kauai.
Accomodations:
We've stayed from locations such as the Hyatt in Poipu and the Ko'Olina resort in Kapa'a, to the small Old Mission B&B in Hanalei to a private rental cottage (basically a backyard rental house for $75/night) in a "sub-division" up on Sleeping Giant Mountain. We have always vowed never to stay in Princeville. It is run by Westin Hotels - the same folks that run the Swan at WDW - and we personally feel it is too "uppity touristy" and feel it really doesn't give you a feel for the island locals and culture. The whole Princeville area is designed for people who can afford a million dollar second home and golf course area. It's where the wealthy elite of the island live. One place we'd love to stay is the Plantations in Waimea. It's all the way on the West side of the island, but has the most amazing atmosphere.
Food: The bakery by the lighthouse up in Kilaheua is great. Just down the main road from there - on the south side of an "offramp" as the road curves south, an older couple run a little "place" just outside their house - more like a gazebo in their yard. The sign on the kitchen building says "malasadas" which are Hawaiian donuts, but they make the best kalua pig I have ever had. The husband has some wonderful stories, too. It's truly a local place - like the fish market in Koloa Town - which also has an excellent plate lunch and terrific poke. The shrimp wagon in Kapa'a is a tasty treat, as well. all locally caught shrimp and lots of garlic!!! If you want Gourmet - go to Pacific Cafe in Kapa'a - in the same plaza with the Wyland gallery and the Safeway. Fabulous dining and they stay open later than most restaurants. Also the sushi bar at Lemongrass had really good poke, too. Poke is a very Hawaiian dish - if you love sushi and raw ahi tuna, this is especially for you. Ahi tossed in a dressing of soy (shoyu) and sesame oil with a touch of seaweed, green onion and hawaiian salt. You can also get it at the Koloa Town Fish market made with smoked marlin or octopus (tako), if you liked cooked fish. There is also a branch of the world famous Roy's in Poipu - never a bad meal.
Outfitters Kauai runs the Zip line and lower kayaking trips up the river into the heart of the island. There are places only they as a company are allowed to go and conduct tours into. They have other tours and we loved them. The botanical gardens on the north end is great, too and you can kayak the Hanalei River, if you aren't brave enough for the ocean. We've wanted to do the tubing trip down the old sugar plantation irrigation canals, but the girls aren't old enough yet. The SNUBA experience was fun. We like to go to Hanalei Bay to just swim and hang out. Surf is very calm and it is a very friendly local beach. Most tourists go all the way to the end of the road at the north so they can see Bali Hai. Another thing we like to do in the evenings is take in a movie at the theater in Waimea. It's a small town theater, but if you get there early enough for the show, they have wicker lounge chairs in the back of the main section - a very homey and comfortable way to see the show and a fabulous way to meet the locals. We actually have a shopkeeper/aunty that we talk to on all of our visits and she came to the show to hang out with us! Very fun. I also make sure I go to Island Soap Works, the quilt shop and the coffee plantation on our trips, although Kauai coffee takes some getting used to.
One caution - It's a very safe and friendly island - but you will still need to be smart and take procautions against petty cash theft crimes, especially if you stay at some of the smaller timeshare places and get a first floor unit - lock your doors - especially if you step down to the beach when you first wake up at 4 or 5 am on that first morning.
The spa at the Hyatt is another do not miss, as is their lobby. They have local entertainment and hula shows there every afternoon at the bar by the big window oposite the entrance, so it's a wonderful, intimate place to sit and enjoy a drink and the sunset. Once you enter the place you understand why it costs so much - OMG - the view when you walk in takes your breath away! Tidepools was very tasty. The Italian place -not so much at all.....
Also, steer clear of the places that offer you discounts on touring tickets and special ocean sightseeing prices - they are 99.9% of the time linked to being forced to sit through a timeshare presentation with a high pressure sales pitch. DON"T DO IT - NO MATTER HOW GOOD THE TICKET PRICE IS!!!!! You don't want to forever regret going to Hawaii because you are now stuck with a timeshare that they wouldn't allow you to say no to. These are all over the islands, so you will be constantly around them.
FYI - the Disney resort will be a Disney Vacation Club development. Not all-inclusive, but like the other DVC resorts on Disney property - especially like those on Hilton Head SC and Vero Beach FL. Land has been broken for it in Ko'Olina on the west coast of Oahu.