Day out to Waimea
First, you visit the head up the Kamehameha Highway and visit the spot where the 1946 tsunami punched a hole in a rock. Awesome power and an amazing spot. It is just across from the Polynesian Cultural Center.
Then, Waimea Valley "Audubon":http://www.audubon.org/local/sanctuary/Brochures/Waimea.html "Center":http://oahu.aloha-hawaii.com/tours/waimea+valley,+oahu/. Its a cool spot where you walk up half a mile to a great pool where you can go swimming. !>http://oahu.aloha-hawaii.com/assets/images/articles/135_main_1.jpg!
Lunch is down below. They have authentic root beer, "pineapple":http://starbulletin.com/2004/08/18/features/story1.html and other sodas made right on the island. They make a whopping 300 cases a week in a single room at the "Waialua Soda Works":http://www.waialuasodaworks.com/. !