Many of the relatives on my side of the family that are invited to our wedding are VERY religious/conservative. I grew up this way too, so I can somewhat understand where they are coming from, but my immediate family and I have loosened up quite a bit in recent years. My concern is that, for personal reasons, my extended family might RSVP for the wedding, come for the ceremony, but not stay for the dinner, drinks and dancing that follows. My fiance and I are providing an open bar for the entire evening (including the cocktail hour) as well as a buffet, and DJ for the reception. I know that my conservative extended family members are not comfortable around drinking and/or non-christian music.
What would be a good way to make sure that they realize we are paying per person for the food and drinks, so if they RSVP and then leave after the ceremony it is costing us quite a bit of money for no reason?