hi tamara ,welcome to healthcare magic forum!
since how long have all the 3 of u been having this cough?did it start at the same time in all 3??
do investigate if something in your house could be irritating the 3 of ul eg dusty curtains ,carpets,a pet or maybe a plant.also rule out a family history of asthma
u may try to releive the cough by natural remedies eg honey and lime or some cough syrup.keep ur child warm.please see a doctor if the cough persitts for more than 2 weeks and if ur child develops fever
or difficulty in breathing to rule out any infection.
in case a lot of people around u are suffering from this it could be an infection and u may need to see a paediatrician.
bye for now