For camping at in the Redwoods, I recommend Ancient Redwoods RV Park on the Avenue of the Giants. Great park, friendly hosts, big rig friendly and right on the Ave.
Hwy 20 is an easy drive. They had a big fire there a few years ago and still show some burn areas. There's a casino in Clear Lake, (which isn't very clear, btw) and they have an off site RV park called Aurora. Great little park. The mgr grows his own tomatoes and you're welcome to help yourself. Full hookups, right across the street from the lake. Gas station near the casino has the cheapest prices.
For camping at Yosemite, try Yosemite Lakes. It's an Encore Park, TT/ELS, but open to the public. It's about 4 miles to the Park Entrance.
Also, while you're in the area, look at Klamath River RV Park. Awesome park, right on the river near the mouth where it joins the Pacific Ocean. All grassy sites with full hookups. Big rig friendly.
Ancient Redwoods RV ParkAurora RV ParkYosemite Lakes RV ParkKlamath River RV Park
