Dear Jacath I think you are right. Your grand son most likely got viral gastro enteritis
The most suspected is Rota virus. the treatment is conservative i.e. to keep the hydration
well. I think you ger Electrol sachet. Dissolve i sachet in 300mls of boiled and cooled water and feed him
frequently at leasr for 24 hours. Srop giving him normal food. After 24 hours slowly go back
to normal diet. If vomiting
continues I strongly advise to take the child to hospital.
Kindest regards Dr. S.K.Mukherjee