Thank you for your query on Healthcare Magic.
Your grand children needs physical examination to look the throat and lungs by a pediatrician
This type of cough
will effect their normal sleep, growth, and activity.
At home, you can give steam inhalation.
They need medication for treating the cough by mucolytic
have no role in this type of cough.
I advise you to consult the pediatrician for examination and for medication.
Hope I have answered your query.