3 hours drive gives me a big stretch of the California Coast as options, to the east, Yosemite. Too many options to choose.
Last few years my wife have been doing day trips, some actually overnight trips just to state parks.California absolutely rules for day trips. We lived in Sunnyvale for a few years in the late 90s......we took so many road trips on weekends.
SameThe Jersey shore (Ocean City , Avalon , Cape May or Stone Harbor), Lancaster, PA or Alexandria, VA.