I have some other possibilities in mind, but first let me ask: where's your second night destination? On the coast, or at one of the BLM campgrounds along the Nestucca? Let me know before I float suggestions that are moot...
Second night's destination is Cape Lookout State Park. That's about 125 kms (75mi) from Champoeg State Park. That will be a full day. Our problem is we don't get to Union Station in Portland until 3pm. We want to chew off some miles on the first day to shorten the distance to the coast on the second. Champoeg State Park or Newberg seemed a good compromise distance.
Thanks for your help!