I'd defintely do hwy 97 in one direction and the Oregon Coast in the other. We're taking 97 south on a trip to Reno next month (and back up the coast). Lots of CGs along 97 to choose from, slower paced than I-5, more scenery to see. Sounds like you will be on 97 for part of it.
If going up to Wa., I'd put a visit to Mt. St. Helens on the list (south side). Mt. Ranier is a nice drive up on a clear day. Leavenworth would be a nice place to visit if you get up that way, and then west towards Seattle over Stevens Pass. (Stay away from Seattle 'cuz traffic is ugly) A trip on a Wa. state ferry is a must-do if you can.
A Portland resident told me a couple of months ago that a drive along the Columbia River Gorge between Portland and The Dalles is a great trip. I can't recall exactly what he said, but there is zip-lining, bungee jumping or hang-gliding there somewhere.
If it happens to be anywhere near your route, Howard Prairie Lake CG between Medford and Klammath Falls is nice. It's in Rogue River National Forest. Been there twice now.
