Except for Enchanted Forest and the Spruce Goose most of those I listed are going to be about an hour or more from Corvalis.
Stay in Portland if you can...I'd reccomend the Hotel Lucia in the spirit of swank
More economical Hotels can be found out near Troutdale(about 20 minutes East of Downtown) which is not a bad place to stay if you plan on seeing the Multnomah Falls or Mt. Hood....but it is less convenient to much of everything else.
Also wish to amend my list:
Mt St. Helens Drive north on I-5 to Woodland then follow the St. Helens National Monument signs. If you have a full day try to go up to the North side of the volcano to the Windy Ridge Lookout---it is quite eerie.
Beverely Cleary Sculpture Garden Portlands most famous childrens author is celebrated at this wonderful, whimsical little spot in Grant Park in NE Portland.