You need to define your request a little closer. If you want Redwoods National Parks, then you need a motel/rental between Eureka and Crescent City. The nearest timeshare is 5 or so hours away.
The Redwood National Park is actually a combination of the National and some State Parks. There are additional state parks from Big Sur to Oregon along the coast that also have groves of Redwoods. The ones near Monterey (Big Sur or north of Santa Cruz) all were hit by recent fires so you will want to check access. Big Basin State park near Santa Cruz was a nice option, but I know they got hit by fire last year so am not sure what their status is.
The state park that is the most like the national park, outside of the NP, is Humboldt SP south of Eureka. It has the Avenue of the Giants drive with many hikes (long or short) through the Redwood groves. It's 3+- hours from either Windsor or Pt Arena timeshares so doable on a long day.
There are smaller state parks that are closer to timeshares as well. Pt Arena is pretty close (half an hour?) to Navarro River Redwoods SP (check for flooding as it's a low area near the river and along the coast).
There are some state parks closer to Windsor as well, but the closest one (Armstrong Redwoods) is still closed due to fire from last summer.
Worldmark Windsor is a large complex and the most likely to get a trade. WM deposits mostly off season weeks which is actually good for the redwoods.
Pt Arena is a former campground with single wide trailers that were remodeled or new about 10-15 years ago. They are very nice, but small at only 400 sq ft. 2 people MAX and only if they are sharing the bed. I have seen families with multiple kids and don't know how they do it. The sofa sleeper is a small one that fills the entire living room when open; nobody is leaving the place when that bed is open. However, for 1 or 2 it's a nice place; nothing fancy but it's the only timeshare on the Mendocino Coast so location, location, location. Compared to the cost of other lodging on the coast, they are a steal. There are lots of deposits here and you can get a real bargain in the off season via Extra Vacations. I've been there spring, fall and winter and enjoyed each stay.