My and some buddies from high school did an 8 day road trip from WA to southern Cali. I would recommend hitting Crater Lake National Park on your way up. We did that and camped there and even with pretty cold temperatures the beauty of the lake is incredible.

Like others have said, drive up the Cali coast as much as possible. There was this black sands beach in the Redwoods National Park via HWY 101 that was probably the most beautiful stop on our trip (minus Yosemite).

Camping and hiking is gonna be challenging in this month, but I strongly recommend checking out the Olympic Peninsula and the national parks that are on the west side of Washington. If you have time, there are some incredible hikes east of Seattle (Mt. Si, Poopoo Point, Mailbox, etc) all of which are doable (but very hard) even in winter.

Good luck, also sightseeing in between your planned stops makes the drive less boring!