Considering you are interested in overnights/weekends when there is the chance for more familiy issues to creep up I think I would be inclined to pass on this one. Even if the caregiver doesn't think she is bringing the baggage of her relationships to the daycare with her she is. It will be reflected in her motivation, her level of concentration meaning supervision could be effected. You will have no control over the environment.
You would probably do better to contact the high schools or community colleges in your area and find a student willing to stay overnight with your child and then get them off to school the next day or ideally you would be home before the student themselves would need to leave for school.