Hello, 
Thanks for the query to H.C.M. Forum. 
As you mentioned that immediately after meal you have to go for 
diarrhea. 
After meal ingestion,colonic phasic & tonic contractility increase for a period of approximately 2 hours. The initial phase ( about 10 minutes as you stated in your case) is mediated by the 
vagus nerve in response to mechanical distension of stomach.
So this is the main point that vagus nerve stimulated due to stomach distension immediate after meal.
This increase the motility of intestine and there develop diarrhea . 
Since this is from 4  years after birth of your child .  May be due to ,
1 Secretory causes , diagnosis can be confirmed by examination of various electrolytes . As  
electrolyte imbalance is the main cause in this group.
2 Osmotic causes osmotic diarrhea occurs when ingested carbohydrates develops 
allergy . Diagnosis can be confirmed by physical as well clinical history of patient so consult a physician and get his opinion. 
3 fat 
malabsorption is the another cause after 
gall bladder removal . 
So in my opinion 
consult a gastroenterologist and get his opinion. 
Till use banana , rice fat free cured, luke warm  water. 
Good luck. Dr. HET