You didn’t mention what time of year you were planning your trip, but their are two times of year that Gray whales migrate along the Oregon Coast. They travel south during the winter, with mid-December to mid-January beginning the typical peak of migration along the Oregon Coast. The last week of December there is a coast wide program called Whale Watching Spoken Here with volunteers at dozens of the top whale watching locations to help assist visitors in spotting them. The whales return north in early spring with the peak of the migration between March and April. The Spring Whale Watching Spoken Here program is the last week in March.
There are also resident whales that might be spotted year-round. Your best bet would be to visit the Whale Watching Center in Depoe Bay, an area the whales are known to frequent.
If you plan on doing a fair amount of hiking on your trip, I would definitely plan on two weeks.
A pretty spectacular start to your journey would be Ecola State Park at the north end of Cannon Beach. You’ll have great panoramic views of the local icon Haystack Rock and the Tillamook Rock Lighthouse just offshore. There are several hiking trails within the park. Cannon Beach is a cute upscale beach town with an easy to walk downtown filled with boutiques and art galleries. Haystack Rock is known for its easily accessible tidepools and at many low tides the Haystack Rock Awareness Program is on the beach offering interpretive information on tidepools and nesting seabirds including puffins during the spring and summer.
About 10 minutes to the south is Oswald West State Park with more hiking trails. I would recommend the Cape Falcon trail, that is just under five miles roundtrip to the end of the cape and back (a great whale watching spot!). Just a couple minutes to the north on the highway, you climb Neahkahnie Mountain where several highway turnouts offer expansive views hundreds of feet about the surf (another great whale watching location!). There is a nice campground a little further south at Nehalem Bay State Park.
As you continue south, you may want to stop at the Tillamook County Creamery, home of Tillamook Cheese, one of the region’s best known products. Then, I’d make a sidetrip off Highway 101, following signs to Cape Meares and the Three Capes Scenic Route. Cape Meares is just a few minutes away where Cape Meares State Park offers great views and a short walk to a historic lighthouse. Your next stop would be Cape Lookout State Park. This would be another great camping spot with adjacent hiking trails. The last cape on the sidetrip is Cape Kiwanda in Pacific City, a sculpted sandstone headland with a giant sand dune on its flank and just offshore is another of Oregon’s Haystack Rocks. You rejoin the highway just south of Pacific City.
The drive between Lincoln City and Newport will offer many views. I’d stop at Boiler Bay State Wayside and the town of Depoe Bay (whales!). Make another off the highway trip to Otter Rock and Devil’s Punchbowl State Park. Just a little further south, you can make Beverly Beach State Park another camping destination before you continue toward Newport. Take time to visit Yaquina Head Outstanding Natural area just north of Newport. There are great views, bird watching, whale watching, a beautiful lighthouse and, if you plan your visit for a good low tide, an incredible tidepool area. In Newport, be sure to visit the Bayfront area and you should probably set aside a minimum of two hours for the Oregon Coast Aquarium.
As you continue south, you may want to make time for a visit to the beach at Seal Rock for more tidepools, then set your sights on the Cape Perpetua Natural Area just south of Yachats. You’ll find some great hiking and beach areas there.
Further south, I’d camp at Honeyman State Park in Florence, offering access to sand dunes and for dune hiking you may also want to stop at the John Dellenback Dunes Trail south of Reedsport.