Was just thinking what I just read reggio post: RED FLAG! If I was to be completely honest with you, I say, NEXT!...these girls are too old for the group you currently have. They will require different activities and have VERY different interests than your current group, IMO too much on your part to keep ALL kids happy and satisfied during their time in your care. I would move on to the next call and wait out for a better fit in age. That being said, IF you nee dthe cash or feel up to the chalenge? more power to you, it can be done, just takes a lot more patience and effort on your part to please that many dif ages.
That is not the red flag though...the fact that the mother is trying to push you to change the way you run YOUR business to better accomidate HER needs is the red flag! I wouldn't do it, if you didn't already have plans to become registered, don't do it for this family, chances are, they only need care for a year tops and then the kids will be home alone given in another year the oldest one will be 12, close to ability to be home for an hour or so after school with out Mom.