You could come up the Columbia River Gorge and then hit US 97 to go south.
I like the Washington side WA 14, rather then the Oregon side I-84. Wa side is a two lane twisty road but has many views. Cape Horn sticks out over cliff looking down on the Columbia. Beacon Rock east of Cape Horn is a wonder to see how it jets up out of the surrounding land.
North Bonneville Dam and visitors center is good for short stop. Lots of parking west of the dam. Good place for lunch or even over night.
I would continue east and cross at Biggs junction.
There is several campgrounds along the route.
You can see these points with out any problems. Parking lots are fairly large.
US 97 is a good highway all the way into CA. Two lanes or more. Several sites to see on and just off US 97.
