Portland Road Bike: Country ride wanted

So, here's the deal.  My husband and I are pretty fit.  We signed up to do the STP with my sister and brother-in-law this year. However, we are so stinking busy we never get to ride.  So this 4th of July we want to take off and get some miles under our belts. And take the baby too!! Anyone know of a good route that is low traffic, fairly close to Portland and has camping along the way?