Yup ... Pull up or diaper at nap time ... If they won't supply I would get some of the cheapest ones I could find or a plastic pant over the undies and when the undies go home wet everyday they will see the reality. Or duct tape a large garbage over the mattress of the play pen and then put the sheet over top and send them the wet bedding and clothes everyday .... Ask them to wash them and return them for the next day ....