Westport Light State Park (www.parks.wa.gov [1]), about a mile south of Westhaven [2] off Highway 105 (continue straight when 105 goes left), is a day-use park good for kite flying, rockhounding, and fishing for ocean perch, but no camping.
A paved, mile-long Dune Interpretive Trail wanders through the dunes, providing several observation platforms that overlook the water. There’s vehicular beach access here, but the sand is considerably softer than at other drivable beaches; be careful if you don’t have four-wheel drive. Check with the park for regulations on beach driving, since some sections are closed part or all of the year.
The classic lighthouse inside the park—the tallest on the West Coast—was built in 1898 and is visible from an observation platform on Ocean Avenue. The building is closed to the public, but tours may be offered by the museum. The lighthouse originally stood much closer to the water, but the accretion of sand has pushed the beachfront seaward.
Links:
[1] http://www.parks.wa.gov
[2] http://www.moon.com/destinations/washington/olympic-peninsula-and-the-coast/grays-harbor/westport/sights/westhaven-state-park