DianaJ
Hi, from Brookings to Florence will run you about 3hrs, at just over 150miles,
Florence to Cannon beach, almost exactly the same. According to mapblast, the first leg of your trip would be 154miles, and the second will be 159miles.

And I gotta say, your second part is gonna be a very very difficult drive. I myself, even after several years of driving it find it quite challenging. See, the problem is, the coastline is incredible. Its hard to tear your eyes away from it to watch where youre going.
Tiffany