You will see that there are no complaints about the Oregon coast trip you are planning. Only great tips.
The only thing I want to add....is plan to go to the coast at the north end of the state. That will have the water and views on your right as you drive down. Going the other way, has you having to cross the highway often...like every 2 or 3 miles...to go look and that is a tough bit of pavement. Getting off the highway is not so bad but getting back into traffic is bad...even dangerous because people see an RV as an obstacle to NOT allow in. Even other RV'rs will accelerate to get in front of you as you are trying to pull out thru traffic and into the north-bound traffic flow. I kid you not and have done the drive many many times.
Yes..reservations in State parks. They are truly the best. There will be no boondocking to be found. (there are a coupe of beaches where there is parking lot camping and a couple of highway rest areas but as was said..August? ha...
Book as soon as you can to avoid the camp ground grind. (That's driving in and out of every campground looking for a vacancy.) There are only a few cg's at the beach, so do your research now.
http://www.oregonstateparks.org/index.cfm?do=visit.dsp_findGary Haupt