Depending on your timing you could go to the Skagit Valley Tulip Festival, then hike around Bellingham (Oyster Dome is a good easy hike.) There’s also lots of great islands to explore by car with shorter hikes (Deception Pass and Whidbey Island). If you want a proper multi day road trip, Olympic National Park makes sense and is very unique to PNW. You can visit the beaches, Hoh Rainforest, Lake Quinault and/or Lake Crescent. However food and lodging options are quite limited.