I'm no expert, and I didn't stay in a Holiday inn Express last night but I'll do my best.
I highly recommend
Matsumoto shave ice in Haleiwa. It's on the north shore, and a bit of a haul but if memory serves, the
Dole pineapple plantation visitor center was on the way, and while touristy it was worth a stop.
I found that local food tends to be cheaper than mainland fare. McDonalds even has food only available in the islands, such as Portugese sausage with rice and eggs for breakfast ( My own personal favorite,you get a platter of food and a large coffee for roughly the same $$ as an egg mcmuffin & a coke) Check out grocery stores in small outlying towns for their deli counter lunch specials referred to as,"Plate lunch" or "Box Lunch"
Pearl Harbor/Uss Arizona memorial - this is a no brainer, everyone should visit this site at some point in their life. Also, Punch Bowl National Cemetary is quite moving. The USS Missouri is on display in Pearl Harbor and the guided tour is well worth the price, try to get one of the older tourguides, our guide was a wealth of information and also had a scrapbook of unofficial photos that really added to the tour.
Hanauma Bay natural preserve - on beyond Diamond Head on 72 this is an excellent place for snorkeling/scuba diving, lots to look at.
Here is a basic map that lists a lot of common tourist traps, some worth visiting some not. (map works better when downloaded and opened in a program that allows you to enlarge it)
Oh yeah, and if you just want to lounge on the beach all day, I highly encourage you to visit a home depot or Wal mart and pick up a pound or two of quarter size galvanized washers, fill your swim trunk pockets with them, and covertly spread them in the early morning out in the shallows in the area of beach you plan to lounge on. All the folks with metal detectors hoping to strike it rich will be going nuts. I found this quite entertaining.
Most of all, Have fun
Good times,
blake