Take it from a 10+ year video producer veteran, DSLR's are GREAT for short clips like those in movie (cinema) production where the camera is set up and lights are fired up, sound rolls, camera rolls, action is called, and about 1-3 mins later, "cut" is called and the camera is stopped. AWESOME !!
However, for weddings it's roll camera continuously from grandmothers being seated, procession, ceremony, and finally after an eon of cooking . . the recession occurs, although then they might want the receiving line captured also and thus the camera is off for maybe 10 mins and begins rolling again.
WARNING: In DSLR's the imager gets HOT very quickly and most DSLR's have a recording limit that is short of capturing all the process in one looooooong file. If you only get the vows, sure.
If'n it were me, I'd just grab a GoPro Hero 3 with a nice hand held or body mounted device, which has decent sound and stay close. Or, pick up a nice little Canon HDV 30 or 40 used and believe it or not they get pretty awesome video in HD and not bad audio. Moreover, if you have a lav that lil camera has a mic input. Or you can pick up a shot gun mounted Rode or the like and it will pick up from like 20-30 feet away decently and again plugs into the ext mic port.
HDV cams record to mini DV tapes and I ran a broadcast business for 7 years on them. Bigger cameras of course but the tapes and recording format were the same. The HDV cam serves as a deck and can plug directly into a TV and even has a remote if it hasn't gotten lost (small). Moreover, if you wanna edit the stuff, it digests right into most all NLE video editors including FCP natively wherein again the camera serves as the deck using a firewire cable.
Nice set up and iMovie will run the cams controls as will Pinnacle Studio. Awesome camera. We had the 30 then bought the 40 and loved both of em.