First, let me say congratulations on your idea to store the RV and fly back and forth. Saves days and days crossing the US.
Since you only have three weeks, let me make some suggestions based on your kids ages. And with this limited time frame, I've concentrated primarily on OR. There's obviously lots to see and do in WA also, but I imagine your kids would rather be out exploring rather than sitting in the RV going down the road. Believe me, the list below will keep you busy for the entire three weeks and you'll still feel rushed.
From Redding, head east to Lassen Volcanic NP if you haven't been there. Hike to the top of Mt. Lassen. Visit some of the thermal features at
Devils Kitchen and
Bumpass Hell. Manzanita Lake CG is on the north side of the mountain. No hookups, but flush toilets. Easy access to Manzanita Lake for evening strolls.
From Lassen, head north to Lava Beds NM. Your kids will love poking around the
lava tube caves. Bring flashlights or led headlamps. We also had bicycle helmets to protect our heads. They also lend flashlights at the visitors center. The
campground there says up to 30', but we've seen bigger units in several of the sites. When we were there last, our PUP and 4Runner combined were nearly 40' long.
From Lava Beds, head north to Crater Lake. Plenty has been written here over the years, do a search for more info.
Then it's on to Bend, OR. We like to camp at
Newberry Crater NM. There are NFS CG's around East and Paulina Lakes that are great. These lakes are in the bottom of an old volcano, so it's like camping along the shoreline of Crater Lake. While there, check out the short Obsidian Trail and don't miss the Lava Lands Visitors Center (see the Newbarry guide linked above). We often spend a week in the Bend area.
But when it's time to move on, head north on US 97/197 to The Dalles and the
Columbia River Gorge. As noted, some great hikes to great waterfalls. We camp at
Ainsworth SP. You're close enough to Portland to go to town and restock on supplies and visit this really interesting city.
From Portland, you can head north to Mt. St. Helens, but with only three weeks, you might save this for a later trip that focuses more on just Washington. The routes into Mt. St. Helens aren't quick, so it takes time to visit the park.
Then it's to the coast. The northern OR coast, being closer to Portland, is busier and has more shops, restaurants, etc. Our favorite part of the coast is from about Lincoln City on south (just because we like fewer people). Of course the Tillamook Cheese factory with it's tours and ice cream is north of this, so you'll have to decide where to start your OR coast tour. There are so many great CG's along the OR coast. Beachside SP, Sunset Bay SP, Tlllicum NFS CG,
the Oregon Dunes National Recreation Area, Harris Beach SP. Many have easy beach access. Of course the beaches aren't so much for swimming (BRRR :E ) as they are for beachcombing.
Some brochures for the Oregon Coast:
LighthousesTidal Pools (Get a
tide table and try to visit the pools at the lowest tide possible).
From Harris Beach SP in southern OR, you can day trip to the Redwoods of Northern CA. By this time, you'll be out of time and it's time for the long drive back to San Diego.
If you follow all my links, you'll find a wealth of information that will make your trip much more informed and enjoyable.
Ken & Allison
2 Camping Cats (1 diabetic)
1996 4Runner, TRD Supercharger, Edelbrock headers
2007 Fleetwood Arcadia, Honda EU2000i
4 mountain bikes, 1 canoe, 4 tents, 8 sleeping bags, 2 backpacks
(You get the idea!)