Epigastric hernias are defects in the midline fascia (the connective tissue of the abdominal wall) usually in the midline, and above the belly button. Most of the time, they are "corked" with a little blob of fat, in which case they are called "epiploceles." Sometimes, the child will actually have a lipoma, or funny round fatty mass (not cancer) that sits above the fascia and mimics a hernia. Other times, the patient will have a raised ridge along the entire midline above the umbilicus, and between the "six-pack" muscles of the abdomen; this is a "diastasis recti." Repair of epigastric hernias in children is a bit controversial. Lipomas usually do not need removal unless bothersome, and diastasis is rarely (if ever) repaired in children.
A surgeon should offer an operation when the risk of operating is less than the risk of not operating. Things that make NOT operating more risky in this case would include:
--a symptomatic hernia: painful, bothersome
--a hernia that demonstrated risk of trapping the bowel (rare with epigastric hernias), like the need to manually force bowel back through the hernia in the abdomen
--a hernia that was growing over the months, and therefore likely to become a problem rather than close spontaneously
In general, a small, asymptomatic, non-growing epigastric hernia can be watched.
So my advice in general is to consider the operation whenever it will a) relieve symptoms or b) prevent problems. If there are no symptoms, and there is little or no risk of problems, then the low risk route is to wait.