Thanks for the inputs so far guys. Looks like I may have to re-think the desire to be only an hour or two from Seattle the last few days of the trip. It's looking like that will really limit our options. I didn't realize the traffic was so bad, and thought that would give me a hundred or so mile radius of the city. As I research, it appears The recommendation to stay west of Seattle as recommended may be an option being as how it looks like the ferries dock pretty close to the Hotel where the DW will be staying Wed-Fri of the second week. Are the ferries pretty reliable Mid October?
It looks like the Saltwater State park closes the end of Sept, but the Dash Point SP has spots available big enough for us. I didn't mention our rig is a fifth wheel slightly over 38ft actual length, and right about 13ft 6in in height which means tree branches can be troublesome sometimes. I'm a very experienced mountain driver and quite comfortable in the mountains. I've never been much of a fan of heavy traffic though, especially when towing. The million dollar hwy in CO doesn't bother me, SLC rush hour traffic drives me nuts.
Finally, I lived in England for 9 years, so rain doesn't keep me from enjoying the outdoors That said, I don't seek it out. If we concentrate on the dry side of the cascades, what can we expect temperature wise, and will we still find a lot of great places to sightsee?