Everything all right?
A "demand" that we do not want to hear!
Seriously! avoid this fake application that does not mean anything, if not; "I asked you, I'll put you in a position to not answer me and my conscience is in place!"
Closed questions generally must not lie! And '"almost" obvious, if you really want to know the degree of soddisfazioone of a client; First sympathy, revenue in confidence, ask him something personal, where it comes from, as you have found, let him feel your interest. Then ask if the service worked. Feel that you care about the restaurant, the good of the customer and you are doing everything possible to all functions.
If you do not care to do the caterer then continue with the "all right?" No one ever tells you the truth and simply that customer will not see him anymore.