Spent a lot of time in Oregon and if I were you I'd come in on I84 as you suggested but at Baker City Oregon I'd turn off and take Hwy 26 to John Day and visit the fossil beds, Kam Wah Chung Museum and that area. Its awesome. Then I'd continue on Hw 26 and check out Mount Hood before getting into Portland. Hwy 26 will take you right to Cannon Beach. Going south make sure you stop at Tillamook Creamery and try a double decker ice cream cone in a chocolate dipped waffle cone with sprinkle. (LOL)and any of the State Parks along the coast would be a fine place to camp. When you get to Calif. try to get reservations at Jedediah Smith State Park and spend some time enjoying the redwoods. But then I'd take 199 northeast to I 5 and then cross over to Hw 97 and visit Crater Lake. and then head east picking up 395 to Reno and home