Ditto what Luong says. Just one thing to add...
Redwoods National Park is really no better than the various other state redwood parks in the area (Humboldt, Jedediah Smith, Prairie Creek); it was just what was left of the "good stuff" when the federal government stepped in, after the state park system had preserved the other good bits. My personal favorite of them is Humboldt, with Jed Smith second. Unless you are specifically trying to "collect" national parks, you should research those three state parks too and consider including visits to some of them.
And even if it's not rainy, there can often be ocean fog there at any time of year, so be prepared for at least a little bit of dampness.
Lisa