Just a heads up, not sure when you visitor is coming. The beaches North of Tillamook Head to the mouth of the Columbia River are closed to Razor Clamming from July 15th to September 30th. This covers the Clatsop beaches where 95% of Oregon's Razor Clams are harvested.
Oregonrunner is right the shellfish license covers clams, and crabs, nothing special for Razor Clams. `Hope you are able to get out there and get a few of these taste morsels.