My issue is that mom [and maybe dad?] pulled into the parking lot with the baby in the car. So that is the pivotal moment, IMO.
Was there a day care worker right there, at the car, in that moment, that said they would bring the kids inside?: So the parents ran into the church? If so, I don't think the parents should be held responsible.
But if they ran inside, LEAVING the baby in the car, then it doesn't matter who else they asked---it is still the parents responsibility to make certain the baby was safely inside the church. If they asked someone to bring the baby inside, they still needed to double check. A baby is the parent's responsibility.
It is not an innocent mistake if they left the baby in the car, and went to do the sermon, and didn't check to make sure the baby was safe. Leaving a baby in the car is just as dangerous as leaving a baby by the swimming pool. You wouldnt walk away, go inside and then say you thought someone else was watching your baby. JMO