"Flipped" Wedding/Reception?

I have worked in the wedding industry in New York and this is pretty common. Most likely the venue has lots of experience doing this and have it down to a science- they know that people won't run right out of the room at the end of the ceremony. Usually "at the altar" pictures are taken during the ceremony, not posed afterward, so I wouldn't worry about that. The other possibility is that you could push the tail hour to and hour and a half, so you'd have a little time near the 'altar' before it needed to be moved (keep in mind, though, that the changeover will be happening out of the camera's eye, so it will be a little chaotic0. Any family that will be expected to be in formal pictures should be informed of that fact before the day, and keep in mind that the photographer will be able to set up big pictures (say, the ENTIRE bride's side of the family) later, so great aunt Edna needn't hang out for the entire formal session). Talk to your contact at the venue about your concerns re: where to take pictures, etc. They've done this before, and they no doubt have a way they usually handle this. Don't stress out! Most likely the wedding coordinator or the matre de at the venue will take the responsibility for keeping the day rolling so you can enjoy the day. The people who run the venue do at least one, and often three or four wedding every week. They won't let you crash and burn. Honest.