The redwoods in Oregon are nothing like the redwoods in California, or the redwoods in the National Park portion of the combined Redwood National Park. That's because California and citizens saved the best groves over a hundred years ago. (Before women could vote, Garden Clubs used their husband's money to purchase Redwood Groves.)
Crescent City is the spot you would want to stay for the night, as its between Jedediah Smith Redwood State Park and Prairie Creek Redwood State Park. It's almost a full-service community, but has a 1950s look, because of several past tsunami. The National Park Headquarters are here. Crescent City is about a 6 hour drive to the Portland airport. Be forewarned, California gasoline is about $1/gal more expensive, plus they have sales tax.
Prairie Creek Redwoods State Park has the beautiful Newton B Drury Scenic Parkway, part of the old highway which was abandoned when they created the multi-lane freeway away from the redwoods. The Big Tree is a short flat trail off the parkway, as are trails to other groves and trees. The Cal Barrel Road is steep to walk on, but you could drive up it and walk down, if someone would walk back up to the car. Look in the meadow (prairie) for elk.
Jedediah Smith Redwood State Park has the Stout Grove and the Simpson-Reed Grove which can be driven to. Both are normally crowded. I usually drive a little bit past Simpson Reed on Walker Road for a more quiet walk on the level road with my dog. A few miles west of Stout Grove on the Howland Hill Road is the new Trail of the Titans Grove. This trail has stairs and a boardwalk; how the Park Service wants new trails to be constructed, to protect the soil around the redwoods.
OR-38 and US 101 is the more scenic route to CC. I-5 and US-199 is the faster more direct route. I would suggest driving south on Highway 101, so the views and pull offs will be on your side of the road and you don't have to cross opposing traffic. On 101 you won't see the ocean until Port Orford. South of Brookings, you only see the ocean a couple of short times in California. Here is a mile by mile guide of the Oregon Coast: https://www.oregoncoastmagazine.com/epubs/MxM/Mile-by-Mile-Guide/viewer/desktop/ You may want to take short detours off the highway to see things at the coast like Face Rock State Park at Bandon, Umpqua Lighthouse at Winchester Bay, Cape Blanco Lighthouse, Shore Acres State Park at Coos Bay. On OR-38, about 5 miles east of Reedsport is the Dean Creek Elk Viewing Area. Here are some online guides: https://traveloregon.com/travel-guides/
Because of your late arrival, it might be best for you to drive I-5 to Grants Pass (4 hours from PDX) for the night. You don't want to drive US-199 after dark. The next day visit the Redwoods, then head north on Highway 101 and you'll have a better idea on your timing for a second overnight. I'd suggest the Sunset Oceanfront Motel https://www.sunsetmotel.com/ or the Windemere Motel: https://www.windermereonthebeach.com/ at Bandon, both of which are on the beach and accommodate dogs. If you have problems climbing lots of stairs to access the beach, there is barrier free access at the Bandon South Jetty. I chose Bandon, because it has great sea stacks on the beach and if your timing is right, these have good tidepools. But you may want to only travel as far as Gold Beach for your second night.
If you have time, a couple of interesting things on I-5 are the covered bridge at exit 71 on the east side of the freeway and the Wolf Creek Inn, a stagecoach stop, at exit 76.
