Just be honest that you're going back to work after mat. leave and how many kids you are allowed for DNA. Do not bend your hours on the first client.
I ask all kinds of phone screening questions about hours/backup care/previous daycare/why leaving/personality/eating habits/sleeping/toileting/do they co-sleep or own bed/allergies/medical issues such as asthma/met all developmental milestones/immunized/socialization with other kids/how they discipline/are they on a wait list elsewhere etc. I find the phone conversation is very telling when you hear their responses and if they hesitate when responding to questions etc. Then if I think it's a good fit, I do the in-house interview with the whole family present. Watching the whole family interact can be very interesting as well.