Here is Washington and Oregon, we have some awesome military camps. Jim Creek is nestled in the foothills of the Cascades north of Seattle. It is beautifu, fun for kids, awesome shower/baths and of course mostly drippy weather. Unfortunately, even though Jim Creek was a communication base, cell service is horrid.
And if you like the ocean, Pacific Beach is another goody run by the Navy. Not only are there cabins and a motel and the RV park, there is a great little restaurant. The only problem with it is on a cliff and a steep walk down to the water. Fort Lewis, McChord, and Camp Murray all have RV parks but usually full so call first for reservations. Fairchild in Eastern Washington has a famcamp but I've never been there. Oh and I forgot Whidbey Island has RV parking also and while I've been to the base, I never stayed at the famcamp.
Not to be outdone, Oregon also has a nice little National Guard training base that offers RV parking. Its not much, tiny tiny but a great place to explore the Astoria area and its also right on the ocean. Camp Rilea is on 101.