They usually have a pew like setup for the wedding party off to the side for the Mass stuff where you sit, stand, and kneel.  Like this.  If you do the Mass wedding it can last a long time, like 2 hours, because they shove a whole Mass in the middle of a wedding ceremony.     Never seen a wedding where the bride and groom sit for the marriage part though.  Probably has something to do with cundisuns.