Stayed at Potlatch for 1 night.  We booked last-minute, so there were very few options available anywhere near Seattle.  We thought that we'd be stuck with a miserable site, but Potlatch and site 83 both turned out really well!  The hosts at Potlatch were very sweet and the facilities were clean.  Our site turned out to be quite large and with a decent amount of privacy.  Potlatch State Park's day use and beach area is across the highway, so there's plenty of beach and grass there (but no trails, etc.).