Not sure where McDermitt, Or is.
Champoeg state park is on I-5 probably 35 minutes North of Salem, Or. Excellent for dogs, kids, bikes, etc. Right on the Willamette river. Closest town is St. Paul, I think.
There is a very nice private RV park on the Sacramento river. Not far off the I-5.
We have a spot at the bottom of our property, if you have an interest. There is water and I have a generator handy, if you would like. We are on 26 acres, blackberries are ripe. We are about halfway from Silverton, Or towards Silver Falls state park. Nights are cool, you will not need to run AC. There is also a nice RV park in Silverton.
Dart