We spend some of July and most all of August in the Pacific northwest.
First thing, about your route. The Oregon coast is one of the nicest drives in the country. It is best done from north to south as there are many sights along the coast and the pullouts will be on your right. Otherwise, you would have cross the road each time, and it is one lane in each direction much of the way.
Don't know when or for how long you intend to be in the Northwest, but this will be our eleventh year at the Washington State International Kite Festival in Long Beach Washington, just across the Columbia River and north a few miles from Astoria, Washington. Fliers and kite makers from all over the world. A most colorful event. Third full week of August.
Plan several days to bump down the Oregon Coast.
When you get into California, don't miss the drive through the "Avenue of the Giants". It starts a few miles south of Eureka and takes you through the groves of giant Red Wood trees. Not to be messed.