If you are travelling during the summer months, having reservations will be a must especially along the OR coast.
State parks are absolutely awesome in Oregon. We like Canon Beach but no state park close by. Drive with NO RV into Ecola State PArk near Canon Beach. GREAT views.
Long Beach WA is just across the bridge from Astoria OR and located on the longest peninsula in the US. Beach town, great restaurants and long beach/Boardwalk to walk. Well worth a very short side trip/stay.
Be aware that coastal fog may hinder views along the Oregon coast during summer but usually lifts by 10-11AM. Coastal highway in OR is basically two lane but totally drivable with your RV. Lots of people on the road in summer so with some infrequent curvy and hilly areas, plan on slower travel times.
Favorite non state parks:
Anderson's RV park Long Beach WA
Canon Beach RV Park Canon Beach OR
Winchester Bay RV Park Winchester Oregon
State Park- Beverly Beach near Newport Oregon
It will be a beautiful trip. Enjoy!!!