Drinks at sunset at either the Hau Tree lanai or the House without a Key would be (and frequently are ) high on my list.

Rent some kayaks (or get a double), and kayak out to Flat Island (aka Popoia) and walk around out there.

Get up early (while you are still on your original time zone) and go to Hanauma Bay. Then drive the scenic way to Waimanalo and stop at the overlooks and try to spot whales. Maybe hike out to Mokapu lighthouse

Hurry up and try to get a dinner reservation for V-day if you haven't already, as the best restaurants fill up fast!

Enjoy!