I went 3 days over my due date with DS, natural delivery and I was out shopping within 5 days of his birth, not nearly as full on as a wedding but if all goes well with the birth i think it could be do-able if you have a family member to look after the baby while you do your BM thing and your partner there for support. Make sure you have some good breast pads in and spares and lots and lots of toilet breaks for the bleeding. The problem will be that you don't know how the birth will go or how you will cope with a newborn, could your friend have a backup BM if things don't go to plan? Having the dresses made though might be an issue with that......

Congratulations on your pregnancy, welcome to BB and Good luck with your decision