i agree that pali hwy has a nice, scenic view of the mountains, ocean, chinaman's hut, especially at the pali lookout point.Definitely rent a convertible and just drive around the island. Wear your swimsuit and when you see something interesting stop and just take it in. Pali Highway is beautiful and there are some spots where you can stop and take some beautiful pictures. There is also a pretty good place to eat called Duke's. It is one of, if not the only restaurant, on Waikiki beach. You can also walk around and see some of the great shops near by. Have fun and let us know what you decide to do.
Even if you can't get the convertible on the company dime, it's worth it to shell out the $$ yourself. Seriously! If you can, get it the day before so you can wake up as early as possilbe (before 7am) and then do a drive around the island, if you can make it up North, head to Waimea Beach...if you get there early enough, there might be parking! LOlawesome suggestions! I just wish my company would "okay" the convertible.