We're due for our first big snowstorm on Monday, so thank dog my wife and I are leaving for Hawaii that morning! We've been together since we were in highschool but we've never gone on a real vacation. My wife was born there and has some things she'd like to do, but she hasn't been back for years and I never have. We spent most of what little money we had getting there. We have a place to stay (near Kailua, I believe) and I believe we will have a car, but we won't be leaving Oahu. Neither of us drink, so bars and clubs really aren't our scene.
What are some cheap or free activities that you wouldn't want to skip over there? Are there any good hikes that might not be super crowded?