In addition to Portland and Eugene, Medford (MFR) is also an option as an airport. The drive from Portland to Coos Bay is about 4.25 hours and if you have the time, it could offer the opportunity for more sightseeing. Your options would include traveling down the Oregon Coast, a stop at Silver Falls State Park near Salem or making a visit to Oregon wine country. I am assuredly biased, but choosing an Oregon Coast route would provide the most scenic bang for the buck, especially if you plan an overnight along the coast before continuing to Coos Bay. The route I would choose from Portland would be I-5 south to Albany/Corvallis, then west on US 20 to Newport. This driving route would add less than an hour to your travel time to Coos Bay, but would offer several great options for stops. If you wanted to do the drive in one day, I would limit stops to a few options like Yaquina Head Outstanding Natural Area in Newport, viewpoints at Seal Rock and Devil’s Churn and Cook’s Chasm at the Cape Perpetua Scenic Area. There are several very scenic stretches of roadway along this route. If you wanted to plan an overnight, the town of Yachats would be a good choice and would allow you to linger a little more and potentially add additional stops.
While in Coos Bay, don’t miss the short trips to Cape Arago (three stunning State Parks near the town of Charleston) and the beach and town of Bandon to the south.
Most of the lodging in Coos Bay I would describe as decent mid-range options. The Best Western Holiday Motel is conveniently located in downtown Coos Bay. I usually stay at the Mill Casino Hotel in nearby North Bend when I am in this area even though gaming is of no interest to me.