Sadly ~ it is her space, she is paying for it and is entitled to 'attend' should something change about her plans or what not ~ if the grandparent took 'sick' for example and she needed to send them what would have happened?

Personally this is why I do not 'double book' my spaces when someone says they are going to be away unless I know it is not going to change unexpectedly ~ aka they are OUT OF PROVINCE for a vacation or something and even then the person picking up an extra day was always told 'if something happens and the client needs the spot I will not be able to take Johnny after all "

With the transition child you offered to attend in their place ~ if the other parent is still on mat leave and flexible could they not keep their hours for the visit within the 'after school starts and before school finishes' so that the children are not in attendance at the same time so you are within your ratio of not having more than 5 in attendance at any one time ???