Planning to come to the Big Island in late March for about a week. My husband and I thought we'd spend most of our time at the Sheraton in Kona (primarily reading and relaxing; we both need "down time"), with a couple of days (one night) in the middle in Hilo. Do you recommend we add a day to the Hilo portion? Any special recommendations for sightseeing and dining? Are there any special museums you recommend?