I would recommend you plan your itinerary to base yourself strategically in two places and make day trips north and south from each base. For instance, to explore the South Coast, you could stay in Bandon and spend one day exploring north to the great State Parks southwest of Coos Bay (Shore Acres, Sunset Bay and Cape Arago) and another day going south, perhaps as far as Samuel H Boardman State Park near Brookings. On the Central Coast, you could base your stay in Yachats, then venture north to visit the attractions in Newport like the Oregon Coast Aquarium, the historic bay front and Yaquina Head Outstanding Natural Area. To the south, you could explore the Cape Perpetua Scenic Area, Heceta Head Lighthouse and Florence where you can experience the Oregon Dunes National Recreation Area. If you wanted to explore the North Oregon Coast, you could have a base in Cannon Beach or Manzanita that would offer day tripping north to Ecola State Park, Seaside and Astoria. For a day trip south, I would recommend the Three Capes Scenic Route that begins west of Tillamook and includes Cape Meares, Cape Lookout and Cape Kiwanda.
I hope this helps, but if you narrow down the areas you’d prefer to visit, I may be able to help with some more specific recommendations on itinerary, attractions or lodging based on your interests.