A visit to South Carolina pulls in both directions. On one side are some outstanding sights that bring you closer to the past: the superb historic district in Charleston, Revolutionary War battlefields, restored antebellum plantations. On the other side are the joys of the present: luxurious resorts, sandy beaches, big-name musical entertainment and a huge selection of first-class golf courses. When the kids begin to riot over the prospect of viewing another old building, visitors can appease them with roller coasters, sand castles and water slides. And when you begin to fear that too much relaxation has dulled your brain, you're usually only a short drive from a site that can provide some three-dimensional education about U.S. history.