driving from Portland, OR to San Fran

Miranda Gardens looks lovely, and that's a good location--very easy access to much of what's interesting in that area.

That place looks really nice.  Definitely a lot of things to keep the kids busy, which is always good.

I'd probably stay in Arcata/Eureka, but you already know I'm biased.

Stay in Seattle a day or two!  That's my hometown, so I'm horribly biased, but there really is a lot to do there.  The Pike Place Market is an obvious favorite, but for a bit of nature, you could also take a detour along the Olympic Peninsula.  There are several alternate routes you could take to use the Peninsula to get down to Portland, rather than the (boring, imho) straight shot down I-5.  Enjoy your trip!