For 25 years, the Napa Valley Vintners Association (NVVA) has been raising millions of dollars for local nonprofit groups through its annual auction. But the event was facing an identity crisis despite its success.

Several other wine auctions had cropped up in California over the years, stealing a bit of the NVVA's spotlight. Plus, the three-day event was attracting more and more attendees who cared more about the opening party and hobnobbing with local vintners and chefs than the auction, leading ...