I've hit bits and pieces of the trip you're considering but not necessarily in the same order. This past spring, we started in southern Utah and went north up to Idaho. We made our way northwest to go up to Seattle and then made our way south through Oregon and into California to Anaheim.
Here's our 2017 map:
https://www.rvparky.com/trip/5862748807757824
Since it's a mess, you'll specifically be looking at the red V-Z and then blue A-O.
In southern Utah, the marker is a little off as I couldn't actually make it pick where we stayed which was a horse ranch 1/2 way between Kanab, UT and Page, AZ. It was good in one sense that we could make it to both, but it also meant a 1+ hour drive to get to just about anything. I've learned that my wife refuses to drive much more than that for sight-seeing. So while we were right near Zion and Bryce, we didn't get to explore them like I would have wanted. We did get to see some cool stuff in Page and I got a birthday trip down to the Grand Canyon's North Rim. The horse farm was neat, though.
> Kanab pictures
We made our way up to Moab, UT which is a family favorite. We explored Arches NP, Canyonlands, and Dead Horse Point State Park. As well as other hiking and trails in the area. Ken's Lake was a favorite- cold water and a nice swim. But this was the end of May with it starting to get hot. I've stayed in Moab twice now- first at Archview RV Park (2015) and then at OK RV Park. Archview was more expensive but more scenic.
> Moab pictures (2017)
> Moab pictures (2015)
We kept heading north and got into Salt Lake City. For a non-religious heathen, I surprisingly loved it there (maybe I just really liked civilization!). The city itself was pretty nice though there was quite the homeless population. It was fun to listen to the arguments outside of the temple areas. Good food at a little Mexican restaurant down the street from the KOA we stayed at.
> Salt Lake City pictures
After Salt Lake City, we headed to the tiniest little town I've ever visited. It was literally 3 x 5 streets in size. The gas station was the post office, RV park office, store, restaurant, and fly shop all in one. The RV park was only 20 or so sites. For July 4th, it was the quietest and most chill July 4th I've ever experienced. It was HEAVENLY! From there, we explored Craters of the Moon National Park and went down to Shoshone to check out the falls and an ice cave. We also did some offroad driving up through the mountains- absolutely beautiful.
> Picabo pictures
From there, we started heading north and west with an eye on Seattle. We first stopped for a couple of days in La Grande, OR. We stayed at a place that had a hot spring feed pool. Super weird to swim in hot water.
> La Grande pictures
After La Grande, we kept heading northwest and stopped in Kennewick, WA. We fell into a beautiful park there at Columbia Sun RV Resort. Very nicely manicured and friendly folks. By this point it was mid-July and the pool was normal temperature, thankfully!
> Kennewick pictures
We spent 2 weeks in the Seattle area at Tall Chief RV. This is an Encore park that doesn't have sewer at most of the sites. But it was beautifully wooded and very rustic feeling. Big issue here was the super low voltage. I couldn't run my A/C without my EMS shutting me down. Ultimately, I disabled it a couple of times for sleeping at night and ended up buying a Autoformer to boost voltage. We loved Seattle- parking was tough with a dually but we preferred driving in vs. taking the train. Just be VERY certain of your truck's height.
> Seattle pictures
Afterwards, we headed down to Chehalis, WA to the Thousand Trails park there. Decent place there but a bit overgrown feeling. Again no sewer. We did explore Mount Saint Helens from there. This was a childhood fascination of mine. It was really cool to see up-close.
> Chehalis pictures
Continuing south, we went to Bend, OR where we explored some more lava-related sights. First we hiked the Lava Butte and then the Lava Cave. Another day we headed up to the Obsidian Flow. Really neat stuff.
> Bend pictures
We headed to the coast for the Great American Eclipse and stayed in Lincoln City at a little river-side RV park. It was a beautiful location and fortunately the fog burned off just ahead of the eclipse. We were in totality and were absolutely awed by it.
> Lincoln City pictures
I would have liked to explore the Oregon coast, but we had to keep moving. We were headed for Disneyland for a Halloween event in late September. So we jumped down to Klamath River, CA. This park was nice, but cell service and wifi were non-existent which made working online super hard. But seeing the "big trees" were on my daughter's bucket list. We explored the Redwood State and National Forest for a few days.
> Klamath River pictures
From there, we headed just a little south to Redcrest, CA and stayed right on the Avenue of the Giants. This was uniquely different than the Redwoods park in Klamath that I'm glad we did both. Very awe-inspiring to see trees that were hundreds of years old and taller than you can really mentally grasp. The kids really loved it at each park.
> Redcrest pictures
From there, we supposed to make a bee-line for San Francisco but got hung up with some camper frame issues. We found it at an overnight stop in Cloverdale, CA at the Russian River Thousand Trails park. We ended up staying in the Santa Rosa, CA area for a little more than a week while we dealt with that.
> Cloverdale pictures
San Francisco was incredibly compressed for us. I'd love to spend a month there exploring. The park we stayed at was the San Francisco RV Resort which is little more than a parking lot with wide long spots for RVs. But it served as a great point for exploring the city.
> San Francisco pictures
And then we stopped in Castaic, CA for an overnight while headed for Anaheim. I think this would be a decent place for exploring Los Angeles as it is just north of the city.
> Castaic pictures
Previously (in 2015) we stayed outside of Los Angeles in Acton, CA at Soledad Canyon which is a Thousand Trails park. Soledad Canyon is about 45 minutes outside of the city so it added a good bit of commute time when we would explore. We checked out Hollywood, Venice Beach, and Santa Barbara from here.
> Acton pictures from 2015
And then we landed in Anaheim where we split our stay between Disneyland Hotel and Anaheim RV Park. The RV park wasn't cheap but it's location worked well. We didn't do any exploring outside of going to Disneyland.
> Anaheim pictures
I'm sure that was overwhelming, but I hope you can pickup some useful tidbits!