When it comes to crepes, the amount that should be served per person really depends on the type of crepe being served.  If they are savory crepes, then a single large crepe could easily serve two people.  On the other hand, if they are dessert crepes such as Nutella and banana or strawberry with whipped cream, then it may be better to serve one or two smaller crepes per person.  Of course, if you are serving a variety of sweet and savory crepes, then the amount of each type can vary depending on how much your guests like them.  For example, if there are three different types of savory crepes and two different types of dessert crepes on offer, you may want to serve one savory and one dessert per person for a total of four or five crepes per guest.