Everybody (for good reason) says to get away from Honolulu and visit the *real* Hawaii on practically any of the other islands.

That said, your inbound flight will arrive at Honolulu, and you will likely spend a night there before departure at the end. And possibly more time in the middle.

So.. walk to the top of Diamond Head and enjoy the view (and the exercise). We walked it from our hotel, and took the LONG way (ocean side roads). Much shorter is the back (inland) way up. Of course, practically everyone else was clever and took a bus to the crater, and did the half hour walk from there.

Cheers