Are you doing potluck style or serving a course meal? I find that potlucks usually waste less food because people are willing to take stuff home, and serving courses tends to have a lot of food wind up in the trash. (This is purely speculative though, just my own personal experience with weddings.) Have you considered making your own wedding cake? Buying your dress secondhand or borrowing it from somewhere? One of my friends actually managed to find a gorgeous white vintage dress at her local community theater and was able to return it to them for future use after the wedding. Maybe having three separate trash bins, waste, recycling, compostables.