Kalopa State Park on the Hamakua Coast (northeast) of the Big Island is a find for adventure travelers: The lush park has nature trails for a family picnic stroll, as well as miles-long loop hikes through exotic forests with birdsong for a soundtrack. Campsites are quiet and well-sited and Kalopa's rustic cabins are well-kept and a bargain. Waipio Valley and Hilo are day trips well within reach. This park is lovingly cared for by staffers and volunteers.
The downside? Set above 2,000 feet (on an ancient flow zone from Mauna Kea, still 12,000 feet higher), Kalopa can be chilly. And don't be shocked if it rains. As is the case with all camping in Hawaii, weekdays are best, although Kalopa doesn't get party-time campers like many beach parks. The Hamakua Coast doesn't have any reliable swimming beaches. But campers can find fun in the sun via a day trip to Hapuna Beach Park, and others on the north end of the South Kohala Coast. Hawaii the Big Island Trailblazer guidebook has all the directions.