Weeeell..I'm a heavy RPer, for my toon's 'marriage' (Its refered to as a blood bonding for trolls) A friend of Zui's preformed the ceremony on a cliffside in Stranglethorn. It involved blood spraying, blood drinking, and scarification. So perhaps stay away from tribal traditions, at least troll traditions
But if you're a tauren I'd guess that you would ask the Earth Mother to bless them, have them exchange vows, stuff like that. One thing that our 'wedding' had was the Priestess summoned a messenger spirit to witness the ceremony, and once it was done the spirit delivered the news to the Loa, deceased ancestors, etc.