Get out of Waikiki would be the first thing
If you like hiking, do the Wa'ahila Ridge trail (Mount Olympus). It has a great view of that side of the island from certain areas. If you don't like Hiking go for a drive up Tantalus (back of UH Manoa).
Check out south shore, and the light house at Makapu'u Lighthouse. Then drive over the Pali, and stop at the Pali Lookout and back into Waikiki. That should take about half a day if you hike up the the light house and check it out. There is also a hike up to the pillboxes near Mid Pacific country club(Ka'Iwa Ridge Trail) that has amazing views.
Route looks like this, with the splotches on places I suggested stopping.
Have dinner here if you are taking your wife/gf
http://www.halekulani.com/dining/ If you are going by your self, have a drink at their bar.