I think taking our own car would be better.
Driving from San Diego to Seattle is a phenomenal trip, if you can plan ahead, and stay on the Coast. Up the California coastline gives you access to everything you already know is cool: Santa Barbara, Morro Bay, San Simeon, Big Sur, Monterey Peninsula, Santa Cruz, San Francisco, then up through Sonoma County on 101, and through the northern California coast redwoods, on the way through Eureka and Crescent City.
And then the Oregon Coast brings even more cool places and things to see: Brookings, Bandon, Florence, Newport, Cannon Beach, Seaside, and Astoria, among a lot of other great towns.
Cross over into Washington, and you can explore the southeast coastline, Cape Disappointment (named by Lewis and Clark, for obvious reasons), then through the Long Beach peninsula, cut over through Raymond to Grays Harbor, and head East to find I-5 in the Olympia area, then up to Seattle. From Seattle you're only a couple of hours to Vancouver, BC, the San Juan Islands, the Olympic Peninsula, up over Snoqualmie Pass to some extraordinary scenery in Eastern Washington.
On your return trip, stick to I-5 to save time, and you can still see Mt. St. Helens, Portland, Mt. Hood, the Willamette Valley in Oregon, cool places like Ashland and Grants Pass, by the Rogue River, then Mt. Shasta, Red Bluff and Redding, down through the California Gold Rush country, down the San Jaoquin Valley with its miles of farmland, up over the Grapevine, through the maze of L.A. freeways, (side trip to Beverly Hills?), and further South, back to San Diego.
An excellent vacation, and LOTS more to see and do than you'll ever be able to take in on one trip. Man, I'm tried just talking about it! LOL! :hysterical: