In Volcano I reccommend staying
here or Kilauea Lodge. Have dinner at least once at Kilauea LOdge.
You can rent some pretty nice bikes in Kona and ride up to Hawi on the Ironman route. We rented from Bike Works.
We've stayed in 4 different places on the Kona Coast and would recommend all of them for different reasons.
If they are still doing tours, Arnotts Lodge had some good ones up Mauna Kea and to see the lava flows. You don't have to stay there to do their tours.
Highly encourage getting Wizard Publications
Hawaii The Big Island Revealed as your guidebook.
Veronica