There is a handful of dining options, a couple of stores, and gas stations available in Volcano, so most of your needs should be covered. Kilauea Military Camp, inside the park, also runs a good general store and sells gas. If you can't find what you're looking for, Hilo is about a 35-minute drive away, and the Keeau grocery store and fast-food joints are 25 minutes away.
Many people choose to stay the night in Volcano to see the dramatic glow at the summit vent and to drive to the coast to see the lava flow into the sea. (If you do, bring a fleece or sweater, as temperatures drop at night and mornings are usually cool and misty.) Chain of Craters Road is currently closed about 8 miles below the summit, however, so you will have to travel outside the boundaries of the park to see lava flows.
Since the latest eruption began in 1983, Kilauea Volcano has been adding new land to the Big Island rather steadily—except when a big shelf of recently cooled lava rock suddenly breaks off and crashes into the sea. Sometimes, molten lava will ooze from outbreaks on the southeast flank of Kilauea, until it meets the ocean, cools, and solidifies into a new ragged, rugged stretch of coastline. It's fire, earth, and water: creation at its most elemental. And if you are lucky (volcano permitting) you can watch it happen. If you do nothing else on the Big Island, do the volcano.Hawaii Volcanoes National Park sprawls over 520 square miles and encompasses Kilauea and Mauna Loa, two of the five volcanoes that formed the Big Island nearly half a million years ago.Kilauea, the youngest and most rambunctious of Hawaii's volcanoes, has erupted intermittently at its summit from the 19th century through the present, sometimes slowing to near inactivity.Kilauea's eastern side has been percolating since January 3, 1983, often sending lava downslope into the ocean, primarily from the Puu Oo Vent. The lava flows are generally steady and slow, appearing above ground and disappearing into subterranean lava tubes. And the volcano doesn't only create, it destroys. In the late '80s and early '90s, lava flows engulfed and demolished the coastal town of Kalapana, and homes continue to be lost to slow-moving lava flows to this day.The caldera at the summit of Kilauea is a contrast of lush rainforest surrounding a massive gray and black pit (about 2 miles in diameter) that pushes out plumes of steam and volcanic gas. It is an eerie, awe-inspiring sight.Within and around the caldera are several smaller craters—at this writing Halemaumau Crater was erupting—and excellent hiking trails. Try the moderate Kilauea Iki Crater Rim hike, which takes you around the edge and then down across the floor of the crater. You won't see lava but there is still plenty of steam emitting from cracks in the earth.No matter what you decide to do, Hawaii Volcanoes National Park is a top place to visit in Hawaii. Even if lava-viewing conditions aren't ideal, you can hike and camp amid wide expanses of aa (rough) and pahoehoe (smooth) lava, a fascinating experience. (Be sure to obtain a backcountry pass.)Begin your visit to the park at the Kilauea Visitor Center, which has maps, books, and DVDs; information on trails, ranger-led walks, and special events; and current weather, road, and lava-viewing conditions, as well as bulletins about that day's activities.