If your son is suffering from frequent diarrhea I'd suggest giving him brown rice with a little butter on it to flavor. Of course a lot of home remedies depends on your son's age. If your son is an infant than I'd suggest you boil a handful of brown rice with excess water, drain the water off and give the rice water to him in his bottle.
If your son naturally has large or frequent bowl movements than I wouldn't fool around with nature. Some children just naturally have larger or more bowl movements than others. Most likely it has something to do with his diet. For instance, consuming a lot of diary products can cause changes in bowl movements. Some children may get constipated while others may experience loose stool or diarrhea.
If this is something you are truly concerned with you might want to read what I wrote about Food Allergies and try the food elimination diet. You can read all about it if you press the button marked "Allergy Wisdom" on the left column.
