The above suggestions are great and I'll add a couple, in Waldport on the River is a marina and RV park. Inexpensive but usually available and allows you to cover from Yachats to Newport easily.
Florence has a city park just and I mean just east of Old Florence, one block East. Allows for sightseeing from Winchester Bay to Yachats.
As mentioned, Winchester Bay has two parks, one Douglas County and one private. The private park is great the county park is for dune busters, very noisy all day and evening.
Honeyman is a great park, I took swimming lessons there in 1949. Same area as Florence. Up river from Florence is Cushman, there is a very small park there. The island in the river there was a hideaway for the Greatful Dead in the 60's and 70's. Closer to town is an indian casino, I don't go to casinos and I don't know anything about parking there.
Just east of Lincoln City is Otis, a very small town with one of the best cafes on the coast. Be sure to have breakfast there. Half order of the German potatoes with eggs or what ever.
Fort Clatsop is an easy drive from Fort Stevens and a very interesting reproduction of the Corps of Discovery's winter location. Across the river is a great museum on the history of the river and crossing the Columbia River Bar. You really have to see the river in action in the winter to appreciate the danger there.
In Newport there are several must see's, Rogue Brewery Public House for lunch or dinner, the Newport Aquarium, Hatfield's Marine Science Center, and Old Town Newport. The made in Oregon Shop and Wood Gallery are a couple of our favorite.
Beachcombing in Bayshore at Waldport is cool. Bayshore is a residential development but there is public beach access.
Between Waldport and Florence is Devils Elbow Day use park, Heceta Head Lighthouse, Cape Perpetua and of course the Sea Lion Caves.
Florence has the Dunes, you do not have to pay to drive through...... Just tell the person at the gate you're going out to the jetty to watch the surfers. My nephew surfs there and they had to threaten the State to get access to public property. Only the immediate dunes are in the park.
We love lunch at the Sea Hag in Depot Bay. Many disagree with our choice but their chowder is good. Next door is the taffy place, very good taffy. Other shops can be fun.
Hope this is some more help, have a great time.