Many years ago I did a C172 flight out of Hilo, after taking a low cost commercial flight over to the Big Island. The flight around the volcanoes and over the lava flow where it meets the ocean ranks as one of the best I've done. I didn't have much time, so just phoned ahead, presented at one of the local flying schools, teamed up with one of their CPLs/instructors, and headed off for an hour and a half. Well worth the effort.