Your business, your rules hon!
I would nip this in the bud early with an honest ... my daycare is 'growing' and in order for me to be able to offer a successful program to ALL I need them on the same schedule for naps / meals and so forth because it is impossible to keep awake children quiet enough to allow sleeping children the nap they need. If they cannot RESPECT that and work with you than perhaps this is not the ideal solution and they should seek a program that either does not have nappers in the afternoon or has a program set up that can manage both awake and sleeping children - aka more than ONE adult so that awake children can be taken somewhere else so as to not disturb the sleepers!