We did the Oregon coast a few years ago and the sand rail tour was our favorite part of the whole trip. They take you out in these custom dune buggies that absolutely fly over the sand dunes. Be sure to do the 1 hour tour, you get to see a lot more and the time just flies. Here's a link: http://www.sandland.com/sandrail-tours/

I'd also recommend the Tillamook Cheese Factory tour (love their ice cream). Lastly, there's no sales tax in Oregon, so stock up on gear at the outlet mall.

If you go to Portland, be sure to check out Ringside steakhouse and Voodoo Donuts. Ringside has the best onion rings in the country and their steaks are amazing. Voodoo has the best bacon maple donuts and lots of other funky varieties.