Agree with Sunnydays in the sense that they had options. And since Grandma has been looking after her she may be assisting with the stalling saying oh no she wouldn't be able to handle it. The fact they are paid up - don't be surprised if they ask for an "extension" of their unused time for another week of transition since this one didn't happen.

On a positive note if they are willing to keep her home whenever she is sick one of the main hurdles of childcare is already solved for you so that is a good thing.

Grandparents are great with the kids as babies and then parents often want the kids to have more as they get older and it is hard on the family dynamics to make the change. Even if child is not 100% you could suggest that Grandma come and bring her anyways tomorrow and if she really isn't feeling well just not stay long but it would still give the child a chance to meet the other children and you. Chances are she will be fine from a health standpoint.