I think certain basic day to day precautions like not getting wet in the rain shower and not drinking refrigerated water will help your children to keep away from cough and cold......I have also heard that vitamin C works better against cough and cold.
children must have worn proper clothes and they should be always at little distant away from other children while playing to avoid the communication of diseases.
avoid them to eat much sweets , chocolates, cakes etc which cause cough and avoid having cool items like drinks etc. I mean let them have all these but there should be some limit.
Try to make neem leaves paste and mix turmeric powder in it then make this paste into small tablets.make your children eat one table every month once.
Children should be provided with healthy food to enhance their immunity to fight with diseases.Hand sanatiser should be used as this diseases are communicable.
Prevention though is good process, now-a-day due to different reason the cold & cough are coming so it is better to cure them with medicines such as crocin cold relief and other medicines available in market