S.D.
The Charles Schultz Snoopy Ice Rink and Museum in Santa Rosa is a fun place for kids, both 4 and 8. There are also some cool hikes and tide pools out at the coast in Bodega (30-35 minutes from Santa Rosa). I grew up in Western Sonoma county and it is absolutely beautiful up there this time of year. I think there is some kind of mini amusement park in Guernville (25 minutes from Santa Rosa on the way to Bodega Bay) and Armstrong Redwood is there too (fun walk along the forest floor perhaps). Feel free to contact me directly if you're interested in the area and have questions :-)