It is not appropriate to get sh!tfaced, unless it is your brothers wedding or something like that, which this isn't the case here.  It is ok to be a little sloppy though.
ie. minimal slurred speech, no falling off the bar stools, chairs etc., 
Also, it depends on the couples wishes.  I went to this wedding where the guy's dad didn't even know his son drank.  There was liquor and beer there but we were instructed by the groom to take it "very easy."
So it depends on different factors, but definately do not fall off of a chair, it is not your special day and therefore it is not up to you to stain it for the two people who's day it is.
(I know not you, just speaking in the second person because it works well here)