(Ahem!) No "d" in Shave Ice!
On Oahu- by all means, visit the Arizona- early in the day before lines get long. And visit the Missouri- and the Batfish (sub right next to the Arizona parking lot) But make time for the Iolani Palace- drive up the Pali Hwy, stop a Queen Emma's Summer Palace (small, quiet, worth the stop) and stop up at the Pali overlook (VERY strong winds allatime, lock car, little small time borrowin' going on dere) drive on over to Kanaohe, buy your lady a lei, stop at the bakery for some pu-pu's (munchies- its all good) then pick any beach up beyond Chinaman's Hat. You want Hawaiian shirt? Buy where the local folks do- hit the Sears at Windward Mall in Kaneohe.
Maui- Sunrise at the top of Haleakela. Take a FULL day, drive the road to Hana. No rush, no race. Stop along the way for banana bread (still warm, was on tree yesterday) and a lei from the local youngsters, and LOTS of pictures. Check w/ Activities Warehouse for discount price on helicopter tours, submarine at Lahaina. Worth it.
Big Island- I like Hilo more than Kona side. Take the trip to Hawaii Volcanoes Park- stop at the orchid nursery (or two or three) on the way. Breakfast at Ken's Pancake House in Hilo, visit the Tsunami Park, and the chocolate factory.