J.P.
For traveling with an infant (I traveled with a 3 month old), I would recommend a front carrier - LOVE my Ergo, a sling would even work too, but I found that more cumbersome. If it has no metal, you don't even have to take them off to go through security. I know that you aren't worried about germs, but this would also keep him/her more confined and not be exposed as much, plus, you can wear the baby at the wedding. If your husband is with you, I wouldn't even bother with a carseat on the plane or through security - just check it. Get a hooter hider, and a Blush topless shirt, and you should be good to go. I would change the baby right before getting on the plane, and if possible, wait till you get off, or change him/her across your lap.
Also, for when you get there, I'm not sure where you would have him/her sleep at that time, but I would highly recommend a PeaPod from onestepahead.com. It can fit in your carseat bag when you check it because it folds up so nicely, and you don't have to worry about sleeping arrangements when you get there...just blow up the mattress, and you are ready. Good luck.