If there is award availabiliry, i believe that the agent should be able to book an awaed ticket, but will be at the same cost as an adult and the infant will have his or he own seat
With the removal of YY fares, getting an infant booked is more challenging. Even EY's most expensive fare has the restriction "TICKETS MUST BE ISSUED ON THE STOCK OF EY OR HR " , so AA cannot sell them. I think that you are going to have to go to EY to get an infant ticket. If it will not sell it, may be an issue