Some thoughts. A great campground to stay at while exploring Crater Lake is Collier Memorial State Park and the outside logging museum at the park is great, Elwha Dam RV Park is a awesome park and great base camp for exploring the Oylmpic National Park and take the time to take the Cape Flattery Trail to the farthest West point in the Continental United States.
As far as Washington State Beaches go one of are all time favorite beach is Pacific Beach State Park.
In Oregon Oceanside Beachfront RV Resort, Coos Bay is also one our favorites, If you are traveling with a dog both of the beaches are dog friendly.
Check out Willitts KOA the kids would love this campground and you can splurge and book a site with your own personal hot tub.