This is Mrs.  When I had our last one 6 years ago, doctors said not to take them around crowds for at least 3 months. If there are grade school kids around, chances are that the baby could catch what they are exposed to.  I wouldn't risk it personally.  Nothing worse than a sick newborn.  Just say doctors orders and leave it at that.   If the grandma can't handle it, too bad.  Baby comes first.