Oregon and the Oregon Coast are great that time of year, but August is a big camping month and the coast weather is usually the best of the year as far as sun goes. So many sites get reserved, you need to book any Coast sites NOW! There are some outstanding Oregon State parks along the cost, nearly all of them are great. But some better then others IMHO.
I used to run a Y trip from Eugene to Florence (camping at Honeyman State Park), down 101 to Humbug State park, then into the redwoods camping at Jedediah Smith Redwoods State Park (California not Oregon) or a nearby Fed Campground, then we’d route up to Diamond Lake State Park with day trips to Crater Lake.
If you’re coming in via I84, you can have a great camp at Mary Hill State Park on the Washington site of the Columbia River, you can cross at Hwy 97. The Maryhill Museum and Winery are both good stops if you’re into that.
A few great State Campground are
Ft Stevens State Park, Astoria (far north 101)
Beverly Beach State Park, Newport
Honeyman State Park, Florence
Humbug Mountain State Park (far south 101)
You really can’t go wrong with most Oregon State parks.
Private Campgrounds
We really enjoy Sea Peach RV Resort
The Hatfield Science Center & Aquarium in Newport are great, so is the Rogue Ales Brewery.
The Rogue River Jet boats in Southern Oregon are a good time too, takes off at Gold Beach. Four Seasons RV Resort is up river a few miles and we were able to camp there and the Jet Boat picked us up right from the dock.
You’re RV will be fine along 101 and at the Campgrounds.
The Oregon Coast changes pretty dramatically between North & South, if you can driving the whole 101 is a lot of fun and doesn't take that long.