From there around toward Kailua/Kona, there are Macademia nut groves and processing sites, interesting to visit. And closer to Kailua near the town of Captain Cook and on Kealakekua Bay there is an old Hawaiian sanctuary, kept now as a park. Good for a half-day visit. Famous Kona coffee is grown on the slopes above Kailua, still many small farms there.
To get to or from Pololu Valley, which is the end of the road at the north end of the island, I'd suggest driving Kohala Mountain Road, which runs along the upper slopes on the dry side below the ridge, and comes into Waimea (Kamuela), which is very near the Parker Ranch... another place to visit!
Around on the east (wet) side is Hilo that has a small-town feel and has less tourist development than the dry side. Flights over Kilauea area often originate here, with the sizable airport sharing inter-island duties with Kona airport. Up the Wailuku River from Hilo are a couple of big waterfalls worth a stop.
We're ready to go back any time!