I have twin boys that are right handed and BOTH golf left handed. I tried to switch them over to right handed a few times, but it was obvious that left was more natural for them. I don't know how it happened, but they are both left handed golfers.
Do they throw 'right handed' as well? If they do, then that's a plus: They've never 'learned' to flatten their Left Wrist (as all Lefties do when they throw).
As your young Left Handers learn to strike a Golf Ball, that should make it much easier to keep the Left Wrist Bent during Impact.