I have gone through your query and I can understand your concerns.
probable diagnosis: Food poisoning/gastroenteritis
differential diagnosis: intestinal obstruction
Investigations needed: ultrasound
The symptoms you have mentioned suggest possibility of food poisoning or gastroenteritis.Fever and diarrhea
increases the odds for food poisoning.
But,considering his age we have to rule out some other conditions like intususception.
I would suggest you to consult your family physician.He might require course of antibiotics to compact infection.
As of now you have to rehydrate him by giving ORS,plenty of oral feeds is also advised.probiotic
drugs and anti emetics also might be helpful.
If symptoms persist despite all these, he might require detailed evaluation which include USG abdomen and rarely endoscopic examination.
Hope this information help you.
Wishing you good health.