Head to Lake Del Valle, a five-mile reservoir in the oak hills south of Livermore, to swim off the gravel beaches and sail, then sleep on the shore at the Del Valle Family Campground. Try for one of the 21 full-hookup sites, since generators are banned year-round and the Tri-Valley bakes once you're inland of the Bay fog. The one catch is the gate, which locks after 10 p.m. with no late entry, so time the drive to beat it.
If the hookup pads are taken, the drive-up sites still take a van running on its own batteries. Sites fit rigs from 35 to 80 feet depending on the spot, so length is rarely the problem.
A day up Mount Diablo
Mount Diablo climbs to a 3,849-foot summit east of the valley, and from the stone observation deck the view can run more than 100 miles on a clear day, west past the Diablo Valley Overlook toward the Golden Gate. Treat it as a day trip. The state park caps trailers and motorhomes at 20 feet, so most vans drive up for the summit and come back down to Del Valle for the night. Gates open at 8 a.m. and close at sunset.
Longer trips out of the Tri-Valley
Henry Coe and the Santa Cruz mountains are really a San Jose trip, so start from the San Jose campervan page. Yosemite is a long haul east and a week of its own planning, laid out on the Yosemite campervan page. Livermore Valley pours wine right next door, but a full tasting weekend runs north to Sonoma. And if you want more length or berths than a campervan gives you, the California RV listings cover the bigger rigs.