I had a client like that and no matter what I kept saying they did there own thing. I terminated, for you I would actually ask them to drop off at 10:30 this way there is no napping them and it won't interrupt your lunch. Tell them if they drop off at 11:30 without lunch then an additional fee will be added as you not only miss your break but you are required to make an additional lunch.

When more money is on the line people usually get the message.