I got to agree with what's been said so far - get a professional to do it, so you can enjoy. (Then by all means take your camera and as many photos as you want
).
If you are going to do it, get a GOOD flash, don't use the in camera flash. Get something with a decent guide number, say 50 or even 35 would do at a push, and use bounce flash where possible rather than direct flash. If you have a reflector adapter for the bounce flash even better - it'll give a little twinkle in the eyes but with the soft light of the bounce
.
Use multiple cameras/cards if you can, or at least have them at hand if your main one dies. Borrow a spare flash if you don't have one. Murphy's Law says occasions like this destroy camera gear
!
Make sure
everything is charged, and have chargers with you - you may be able to charge batteries you used in the church during the start of the reception, and so on. It can get a bit testing when the batteries start taking time to charge the flash!
If you have more gear ready and available to you than you think you could possibly need, you might be OK
.
Oh, yeah... sense of humour needs to be in tip top shape.
If you let on that you've got some little niggly problem with the gear, it'll be reflected in the faces of everyone in the photos! You have to make everyone feel good (no pressure, no pressure... that's just the way it is
).
Enjoy.
Al.