I was there for 5 nights and 5 days seeing 2 islands (Big Island - 2 days and Maui 3 days). I researched for about 2 months to decide what my itinerary.
You can do from nothing to everything in Hawaii... Depending on what the interests are, here are my suggestions:
- Big Island Volcano National Park, Do not miss the crater and the Lava Road at the end of the "Trail of Destruction"
- Big Island South Pointe: The real southern most point in USA (Ka Lea). Drive is pretty good except for the last 15 miles when it becomes pretty bumpy.
- Big Island: Saddle Road drive - between the Mauna Lea and Mauna Kea mountains - bit *scary* at night , otherwise its awesome
- Maui: Haleakela crater tour (Sunrise early morning at about 10000 ft)
Avoid: Big Island Downtown: Nothing in it. I wasted an evening there.
Big Island Recommended stays: Hilo (nearer to Volcano) or Kona (fantastic beaches).
For Sight seeing:
- Big Island: Akaka Waterfalls
- If interested in flora, Big Island Botanical Gardens is good.
- Maui: All Maui tour is good, Seven WaterFalls?, City of Hana etc. Maui is just full of waterfalls everytime it rains.
- Helicopter ride in Maui is okay, but bit expensive
- All beaches in Maui are good.
- Sunset Boat Ride is worth it.
If you are taking tours, check a few of them, what their iteneraries are.. Some of them are in a real hurry. I got the Roberts tour, they were decent. I dont know how it is going with kids... you get more time while driving yourself, but have less time to admire the beauty.
- Maui Lahaina is good.
Recommended stays: Anywhere near the Kaanapali area is good. Maui is really really recommended visit.
Beaches: Oahu's Waikiki is good. Problem with Oahu is its too developed near Honolulu areas. The real Hawaii is in Maui and Kauai. Kauai is pretty secluded and you can have a great relaxing time there. There is also a Sanmarga Iraivan Hindu Temple in Kauai.
Other than that you always have surfing, parachuting in several beaches.
There is a Discount card somewhere I bought for $30. This gives upto 15-20% discount in almost everything you buy in hawaii (including tours, shopping center etc). I saved over a $100 with this card. I have to check, dont remember where i got it.
Havent been to Kauai... next time.