I would agree that extreme North is the most scenic. You're relatively close to Waimea Canyon where you're staying so you should consider that if you have another day free. Lot's of switchbacks on the route up so it's relatively slow going. It's referred to as the Grand Canyon of the Pacific and it's aptly named. We always stayed extreme North in the Princeville area and when we went to the canyon it was a trip that needed to be relegated to an entire day with the travel time and stopping to eat, etc.I'll be getting there late on Saturday, but plan to have Sunday as a driving day. I've heard the really scenic part of the island is in the North? Looks like Hanalei Bay is there, so I'll make sure that I get out there then.