I found one website where it gives you many things to do anywhere in California, but you can choose a region and if you choose the northern region you will see a lot to do. I saw you said your interested in camping the Humboldt Bay National Wildlife Refuge has things to do like boating,fishing,hiking,camping, and you can even ride horses, but that's just one place out of the many places to choose from. Here is the link
http://www.visitcalifornia.com/site/...imageField.y=5. Hope you can find something to do and happy birthday to your husband.