We have been to the OR Coast 4 times with the RV and, God willing, will be spending nearly 4 weeks there again this year. In fact, we will be there at exact same time as you. This time will be two weeks in Cannon Beach, 5 days in Newport and then a week in Bandon - we have not stayed in Bandon before and looking forward to that.
No matter what you decide I suggest you make reservations asap; many places may be fully booked already. You are finding that out already.
I know, free advice is worth exactly what you pay for it! :-) But I have found that the vast majority of info on this Forum is good.
We stay at FHU, usually private RV, parks.
We love Cannon Beach area and stay at Cannon Beach RV park. We should be there 8/22 - 9/5 which includes Labor Day. Ecola State Park is just north of town and it wonderful.
Then we go to Newport. The "new" rv park is right at the marina and good. And always go to Tidal Raves in Depot Bay for an early dinner - make a reservation so we can get a window table. With luck, some whale watching, otherwise just ocean crashing on rocks below you.
We have stayed at Winchester Bay at the RV park; one of the nicest places you can find. We are skipping it because, unless you are into dune buggies, there is not a lot to do there. And the beach walking is much better so many other places - you have to drive a bit to get down to the walking area from the rv park. Beautiful place but not much there for us - which is why we are going to try Bandon this year.
Make sure you stop at Tillamook Cheese and have some ice cream and perhaps buy some cheese.
Old Town in Newport is neat - make sure you see the sea lions.
Lots of things to see along the Coast with lots of pulloffs big enuf for your rig or a toad.
For pix, see
www.LaurenBarbara.com and go to Wanderings link on left then to Oregon then to Coast.
Email or PM me if you want more info.
Enjoy - be safe.