can sleeping in ac and air cooler cause any harm to children   

You can make the baby sleep in AC or heater as long as the temperature is thermo comfortable for the baby. This means the temperature should be neither too warm nor too cold. It should be bearable and pleasant. Just make sure that the airflow is not directed towards the baby. The atmosphere in the room should be around 26 degree Celsius which is ideally thermo comfortable for the baby.