The dose of Gravol Kids for a 10-month-old child with gastroenteritis should be calculated based on their weight. It is recommended to give half a suppository every 6 to 8 hours, up to a maximum of 4 times in 24 hours. If the symptoms of gastroenteritis persist for more than 48 hours, it is important to consult a doctor, as dehydration can occur rapidly. It is also advised to give the child milk more frequently but in smaller quantities to prevent dehydration.