You two should be the first to exit the church after the ceremony, followed by your wedding party and parents. Then, it depends on your ceremony schedule. If you plan to take photos at the venue, you could just walk out the front door and then circle back around through a back door to get back in and take pictures. That should give guests enough time to file out of the church. Or, if you plan to have a receiving line, you would want to exit and wait just outside the door to greet guests as they make their way out. Once all the guests have gone through the receiving line, that will be your que to go ahead and make your grande exit.