Oh, also, keep the baby far away from the other kids and make them use hand sanitizer all day long. If an infant gets a fever or ill at all before 7 weeks old, the emergency room doctors (at least at Children's hospital) have a protocol to do a spinal tap!
I know this bc my dd got sick at exactly 7 weeks old and they told me that had she come a day earlier they would have had to do the spinal. It was bad enough that they stuck her over 10 times with needles trying to draw blood but couldnt get a good vein bc she was so small.