To Avoid: Stay away from the cities with the motorhome. Do all your city touring in the car.
Yosemite: We like Yosemite/Maraposa KOA, very large sites, Yosemite like atmosphere about 30 miles outside the park entrance. Indoor heated pool, just very nice.
For the Redwoods, consider Benbow Valley KOA for a basecamp in Garberville. It used to be Benbow Valley Resort and became a lovely KOA. Full 18 hole golf course attached (I don't play, but it's pretty). Really fine restaurant walking distance. The resort is in the heart of the historic Redwood area, often viewed in the old documentaries and Disney programs. Drive through tree, Mystery forest, Redwood RV, etc. This area is best toured in the car. Between the two there are many places to tour. You could head up highway 49 (gold rush country) and stop at the many quant towns. Sacramento has a really fantastic RailRoad museum in old Sac. Vacaville is a great basecamp to visit Napa and wine country. We stay at The Vineyard RV park when in that neighborhood. If you head up highway 99 instead of 49 you pass through Lodi, also wine country, no resort RV parks in that area that I am aware of. If you do want a stop at San Francisco consider Petaluma KOA, a real gem in the KOA franchise, just over the Golden Gate from the harbor tourist area. Enjoy, and Happy Trails.