With a cowboy's demeanour and hands so huge they look as though they're made for crushing cantaloupes, Steve Burgess pours a sticky-sweet concoction from his canteen. He can't help chuckling as he explains to his fellow guests that it was conjured out of a swath of grenache that had been saddled with Noble Rot, and then fortified with local pinot noir brandy. The crown jewel of Burgess Cellars – a small, family-run operation founded by his father Tom in 1972 – is their plush Bordeaux-style cabernet sauvignon. But tonight everyone's talking about this ingenious ambrosia: It tastes like melted strawberry sherbet, with a boozy twang that makes you want to run outside, lie down between the interminable rows of vines, and stare up at Napa's gigantic sky.

Viader Estates & WineryGuests gather for a bacchanalian business dinner at Viader Estates & Winery.

All 18 tanned guests at Viader Estates & Winery, mingling in the cathedral-ceilinged tasting room and drifting outside and onto the wide granite wraparound balcony, come from local wine families that date back two, three and, in some cases, four generations. They call themselves NG, "The Next Generation In Wine," young industry insiders who have been working in the family wine business in Napa since they were old enough to sit on a tractor without falling off. Now they're driving the tractors while trying to figure out the best way to drive the wineries that bear their names into the future, and into an increasingly tight marketplace. If they're supposed to be in competition, it's impossible to tell amid all the laughter and inside jokes and exclamations of, "Man, you have to taste this…"

Viader Estates & WineryTables are set in the Viaders' backyard, the site of many Next Generation supper parties.

"We support each other," Janet Viader says, as she adjusts her nephew's bike helmet before he pedals off past a forest of adult legs. "In a way, it's easy because we all share similar values, and there's a lot of common ground. We understand the pressures of having to work for our family, of having our name on the bottles." The 30-year-old works in sales and marketing for the winery, alongside her mother, Argentine transplant Delia Viader, and her brother Alan, 32, who's manning the outdoor grill, cooking dripping skewers of marinated meats for tacos, and turning spiced, buttered corn on the cob. 

Burgess vintage International Harvester truckGas tank notes are clipped to the dash in the Burgess' vintage International Harvester truck.

Although most NGers have known each other since childhood, these gatherings are somewhat of a new tradition. The 20 or so members meet at one of their wineries every couple of months, and sit down for a glass of wine and a bite to eat. There's talk of experiments in winemaking and in collaborative marketing. For adult children working with their parents, questions of family dynamics, succession planning and how to move forward hang in the air. With the era of modern winemaking in Napa closing in on the half-century mark – Robert Mondavi founded one of the first post-Prohibition wineries in the region in 1965 – a growing number of its winemakers are nearing retirement age. More than half of California's 3,600 wineries will pass from first generation to second in the next few years.

Napa Silverado TrailNapa's Silverado Trail is lined with wineries. 

It only takes a couple of days to see why most of the population here has wine on the brain 24/7 – especially those who've been drinking it since the age of 12. There are down-to-earth people hand-crafting vintages in stunning settings around every bend in the road.

Tom BurgessTom Burgess uses a refractometer to check the sugar levels of the grapes. 

The Valley's oldest winery, Charles Krug, started in 1861. Owned by the fabled Mondavi family, it has a mammoth yearly production of 75,000 cases. Alycia, the great-granddaughter of Italian immigrants Cesare and Rosa Mondavi, greets me in the enormous sun-bleached courtyard with the poise of an heiress but with the heart and humility of a farmer. She describes growing up in the middle of an empire with her three sisters, Angelina, Riana and Giovanna, all in their 20s. "When we were 10 years old, we were paid 25 cents an hour to sit in the sugar shack and pull sugar samples, test pH levels, that kind of thing. The last thing we wanted to be doing was putting in eight-hour days during the summer, instead of being at camp. My parents called it 'an apprenticeship' when it was really more like child labour," she says with a laugh. 

Silverado Trail Napa ValleyThrough the grapevine: Early morning sun illuminates a vineyard on the Silverado Trail, a historic trade route on the eastern edge of Napa Valley. 

Now she's helping lead the renovation of the Krug tasting room, which is moving from a relatively modest-looking shop to a building that's roughly the size of a city church. It's an enormous task, and one that would have sent most twentysomethings running for the hills. But the Mondavis are a rarity when it comes to new-world wines, with four generations under their collective belts.