Here are some ideas. I'll be up front and let you know that I work on rivers in NorCal and Southern Oregon for Momentum River Expeditions www.momentumriverexpeditions.com
1) Which river in Oregon would you recommend (best if the departure was 1 hour or less from an airport)?
We offer the Rogue trip that Wadeinthewater mentioned. I recommend the Lodge to Lodge experience personally,especially in the spring, which is three days two nights. But, we also do a four day camp trip which is great. This trip has some wonderful scenery, historic sites and is basically a class III whitewater experience.
If you wanted to turn it up a notch and have a world class whitewater experience the Cal Salmon/Scott, class IV-V is amazing in the spring. This is a longer drive, three hours from Medford,OR or Redding,CA , but the schedule of rafting accomodates travel time to the remote location.