We would also recommend the state parks. Pick three spots along the coast: northern, middle and lower and sitesee from those areas.
I would also recommend reversing your trip. Where do you want to end up? From Colorado head there first and then work your way back to Colorado. You'll be driving the Oregon coast from north to south and by doing that you will be on the ocean side where all the nice pull-offs are. Then you can easily stop without having to cross traffic on the highway and it will be easier exiting your stops, too. Have a great trip. It's a beauty!