(disclaimer: I've never been to DLR, going first time this December... but I do have a map!)
Looking at my map of DCA, I see an attraction (#40) called "Seasons of the Vine" in the Golden Vine Winery. Description says:
Celebrate California's wine country with the "Seasons of the Vine" presentation.
The Golden Vine Winery looks like it is along the parade route, in the Golden State District, along the back side of the Grizzly River Run.
On the same map, attraction #47 is The Vineyard Room at the Golden Vine Winery. On this "cartoonish" map, it appears to be a separate building.
So, assuming The Vineyard Room is not exactly the same location as the Seasons of the Vine (though they are both in the Golden Vine Winery), and assuming the Visa site's description is correct, then I'd say the M&G is not at The Vineyard Room, but is actually "next door" at an attraction called "Seasons of the Vine."
I'm not sure this helps, because it's not coming from first-hand experience, but I thought I'd share what I found... I too want to know the actual answer.