The definition of edible varies wildly, and never are the stakes higher than at a wedding. The New York Times ran a story this weekend on whether vegetarian brides (and the article refers primarily to brides; grooms are largely nonentities) are obligated to cater to the dietary preferences of meat-eaters. Many (such as Chelsea Clinton) make the concession in the interest of general harmony. Many others do not.
But the article misses a rather obvious contrary point. To paraphrase a friend on Facebook: What about the rather thoughtless meat-eaters who provide nothing for vegetarian guests beyond dinner rolls and lettuce?
Or, to recount a story from a wedding photographer friend, what about those in rural Minnesota who only provide a chicken entrée, thereby depriving guests of "meat"? ("I thought they'd be serving meat," said a number of guests, with completely straight faces. "Where's the meat?")
Speaking as an omnivore, it's your wedding, serve whatever you like and we'll deal with it. I tend to choose the vegetarian option when it's provided, since it'll guarantee that I get to skip the miserable chicken cordon bleu. But if you're meat-eaters, make allowances for your vegetarian guests—meat-eaters can subsist on vegetarian pasta or veggie burgers, but it's not fair to expect those who abstain from meat to have to choose between carb-loading on rolls or passing out on their feet.