I would charge it as a monthly class.  Something like this... class fee 10 dollars or free with a mininum 35 dollar order.  Then do a mystery hostess, each 35 dollar order is a ticket into the draw for all of the hostess benefits from the event.  Draw one person AFTER everyone has ordered, then the hostess of the night can choose her goodies.  It has worked for me in the past.  Also, bring  a guest who has never stamped with you before and receive one extra ticket in to the draw for every new friend.  Good luck!