MagicPenguin
One Thousand Club
Actually, that's mostly the show. While the books do have a solid number of notable deaths, they don't even have a third the "well-known characters" death of the shows. And nobody died at Renly's wedding.
Renly himself died pretty brutally not long after, and his wedding wasn't even experienced by a PoV character, so for all we know, some random minor lordling met his demise in a melee or something. Anyway, weddings in general seem a dangerous prospect in that world, book or show. Two of the weddings in the third book contained the death of a major character (or several major characters, in one case) and at the series' first wedding among the Dothraki, someone outright says something like "The Dorthraki consider a wedding where fewer than five people die to be a dull affair." I think the only wedding so far (that has actually been covered in a PoV chapter) that didn't contain a major death was Tyrion's, and that was a pretty depressing event for all involved (except perhaps Tywin, Cersei, and Joffery) even without any deaths.
I think Dany's wedding in book five may have also been deathless, though someone important was poisoned not long afterward.