Be very careful of saying the reason kids nap two hours is so you can have a two hour break. No one gets two hours off at work either really.
Kids NEED two hours and especially those in daycare who are not getting enough at night by the time parents get them into bed and up in the morning to come to care. When a parent tells me the child is fine on the weekend with no nap I remind them that our pace is a lot faster, nosier and busier than at home by themselves and that I am not able to comfort them one on one to help them cope so they need to be able to do it themselves. With one child yes I can keep them up all day if I keep interacting with them but that is not realistic in group care.
Two issues with the 13 month old - child needs to come earlier in the day so she has playtime instead of arriving at naptime. It would also make sure she isn't being allowed to sleep in till she wants to meaning she is getting her nap just doing it tacked onto the nighttime sleep instead of saving it for afternoon - she may very well not be tired at naptime.