These guys have nailed it above. A few more favorites:
Taking the kids on the ferry (across the lake) at Saddlebag Lake. A low cost way for the fam to get on a boat and cruise to the other side of this lake. Jump off, walk around a bit and get back on when your ready. Round trip is like $11 per adult.
The kids might be a bit young but I'm usually stopping at Camp Manzanar. One of the Japanese relocation camps. The twenty minute movie shown literally brings me to tears every time. All at no charge (donations requested). With a map, you can drive the small property and envision what was where with some remnants of the past. The cemetery that held those that died during this time...babies, children...wow.
Devils Post Pile...
And then there's Mammoth Brewery...FREE beer tasting! Leave the kids in the car (on a cool day!) and go to this one...
Jim