I would recommend you start your coastal tour in Bandon, one of my favorite beaches and small towns on the Oregon Coast. However, the stretch of US 101 between Brookings and Port Orford is also a beautiful drive and passes through the scenic Samuel H. Boardman State Scenic Corridor. Otherwise, Bandon fits nicely with your interest of towns with character — and it has great restaurants (try The Loft or Alloro Wine Bar and Restaurant). Bandon’s beach is one of the most scenic on the Oregon Coast with many rock formations along the shoreline and just offshore. It’s a great beach to walk or view from viewpoints such as Coquille Point or the Face Rock overlook. If you spend a couple days in Bandon, you could consider a day trip south to Cape Blanco and Port Orford. You could also day trip north to to Cape Arago via the Charleston to Bandon Tour Route. Cape Arago is a must whether you make it a day trip or part of your travel north.
Florence has a great old town and good restaurants, so you may want to spend a night there which would give you the option of exploring the Oregon Dunes and then enjoy a leisurely drive north along another beautiful stretch of coast between Florence and Yachats. I would take the entire day for this stretch with must stops at the Heceta Head Lighthouse and several stops within the Cape Perpetua Scenic Area to see Cook’s Chasm/Spouting Horn, Devil’s Churn, beaches, tidepools and views from the top of the cape. Yachats is very small and is less walkable than the other towns on your list, but there are a couple of nice restaurants (Ona is my favorite for casual fine dining).
Newport is a much larger city, but it does have some fun districts that offer the character and restaurants you are after, as well as several must see scenic attractions nearby such as the Yaquina Head Outstanding Natural Area and Devil’s Punchbowl. The historic Nye Beach district and bay front areas are fun to explore and offer good restaurants (my top recommendations include Local Ocean Seafoods or Saffron Salmon on the bayfront and April’s or Sorella at Nye Beach).
Cannon Beach is also a good choice for walkable small towns with character and good restaurants (including the casual and tropical Castaways and the Irish Table among several good options). Cannon Beach has great beaches and State Parks both north and south with Ecola State Park being a must-see. Cannon Beach hosts a wine and culinary festival (Savor Cannon Beach) March 10-13 that might correspond to your travel dates. Cannon Beach also makes a good base for exploring other coastal towns, including Seaside and Astoria, and their attractions. So, as you were thinking, the towns you have identified sound like they are good choices for you. Consider two nights in Bandon, one night in Florence, one night in Yachats, one night in Newport and two nights in Cannon Beach.
You will want to be prepared for rain, but I would expect that you will experience all kinds of weather and spectacular scenery in any case.