Your kid is suffering from gastroenteritis- which is mostly viral in this age group.
For fever, you may give him Acetaminophen
syrup in a dose of 15 mg/ kg/ dose repeated every 6 hrs for 2 to 3 days.
Since its mostly viral, he will not need antibiotics (Oflomac)
Both Rinifol and econorm
have probiotics- that help in reduction of duration and frequency of the loose stools. You may give econorm alone 1/2 sachet twice a day for 5 days.
Take care of his food and fluid intake so that he does not get dehydrated.
See to that he passes urine atleast 4 to 5 times in a day.
Give him plenty of fluid like ORS, plain water, vegetable soups etc
Give him rice based food, banana etc
Avoid fruit juices, cow`s milk for few days.
With this he will be better in a couple of days.
He might develop vomiting
too. In such a case you may give him Domperidone
syrup in a dose of 0.3 mg/kg/dose given thrice a day for 2 to 3 days.
If he has high grade fever, not taking anything orally, you see blood in his stools- then you have to see a Pediatrician
Hope my answer helps you.
Wish your son a speedy recovery.