The only restriction I've heard is that children in approved safety seats may not occupy the row immediately forward or behind an emergency exit row:
AA Approved Infant Seat or Child Restraint Device Seat Locations
If you are using an approved infant seat or child restraint device, please note that it...
May face toward the front or rear of the plane in accordance with instructions on child seat label
May not occupy an exit seat or the row in front of or behind an exit seat
May not occupy the space between a customer and an aisle
http://www.aa.com/i18n/travelInforma...ngRestrictions