It is up to you...but I do feel you should let other families know one of your children has chosen (the parents have) not to be immunized. As that child ages they have the potential to bring something in to the daycare that the younger children are not yet old enough to have the immunizations for. While it is potentially unlikely, they are at greater risk of exposing the youngest children to illnesses that could have been prevented. I think it is worthwhile to inform the other parents so if something is brought into the daycare you can in the least say you had informed everyone and are not liable. Otherwise I do believe some parents may accuse you of creating an environment where young children were put in the position to be exposed to an illness that is typical well protected. I would cover your bases and ensure everyone is informed. I personally would not accept the child into care as I would feel a tad responsible should the non-immunized older child brings in something and it spreads through to the younger children.