Usually the better reason is for a right handed hitter to switch hit. If someone is a good hitter left handed the advatage of switch hitting isn't quite as important.
Reason for this is all switch hitters end up hitting left handed a far greater percentage of ABs.
So unless a hitter becomes equally good both ways. Switch hitting could make him a weaker hitter over all. Even if he is a good right handed hitter and OK left handed, switch hitting becomes a disadvantage because he will be hitting left handed most of the time.
I'm sure everyone knows this, but it is because there are a lot more RHPs than LHPs.
But the good thing is, at your sons age you can try most anything and see what happens.