Just my opinion but Sac has no places to recommend. Don't know how far out you want to be but Auburn has Gold Country RV Park. NICE. 
Vacaville has two older parks, Vineyard and Midway. They are fair places. Then there is Dunnigan, roughly 20 miles north on I-5. Only one we have stayed at is the older one on the west side of the freeway behind the rest area. Sorry but cannot remember the name. It was ok 10 or so years ago. The other two are fairly new and right on the freeway and I don't think there is any shade. Hopefully others will chime in with a bit more info...