It seems as though the age of members and the practice of bringing children to meetings are two different things. If so, your bylaws could target the prohibition of members' young children at meetings.
Or is your guild trying to exclude women who are in the child-rearing phase of their lives? Just not sure based on this thread's title of age limits. If someone had to be 40 to join, it wouldn't guarantee that they are past the child-rearing phase.