UPDATE RE: GIANT WINE BOTTLES
After all my time spent on research for the large format wine bottles, I came into contact with a very nice woman at one of the vineyards. She told me that they kept empty wine bottles after hosting wedding receptions at their vineyard and re-use the bottles by pouring in their own wine at a later date for use.
I also realized that it would be less expensive if I was able to purchase an empty wine bottle. A "VERY" nice winery told me where they purchase their wine bottles from. I contacted the bottling company and they are able to custom make a wine bottle of any size you wish. The largest bottle they have ready for sale and pick up is 18 liters and the cost is $150! To me, this was a fantastic value because I was more concerned about a large bottle than the wine that would be in it. I am planning on having all guests sign the bottle for our souvenir and as an alternative to a guestbook!