Lahaina Maui is a tendered prot, which was it's only detraction. We scheduled a snorkeling tour on the 'Four Winds'. This was not a ships tour, but was very enjoyable. Maui has a great buss transit system, so no rental car was necessary.
We rented a car in Hilo. We drove to Volcanoes national park. The park was interesting and enjoyable. You should do more specific planning for the park than we did. There are many hiking trails, and things to look at. The lava tube was easy to find, and worth seeing.
There is a main road that takes you down near the shore. There is a lot to see down there, such as a natural arch, and a place where the lava flowed over the road. When you get there the road is blocked off, and you have to walk to the sights. The sinage is at best poor. We ended up missing a lot because we didn't know how far we needed to walk, or exactly in which direction. - Be prepared!