I'm another cross-dominant shooter. Rifles and pistols I shoot right handed, just close my left eye. Shotguns, now that's where things are messy. I started shotgunning right handed and was pretty inconsistent. Occasionally I would have to shoot left handed due to the way birds were coming in (geese) and I noticed my shooting improved. Bought my wife a LH 20 ga. and started using it (on upland birds) as she wasn't. I definitely am more consistent shooting birds lefty.
So here's my take. IF the boy is truly left eye dominant, teach him to shoot lefty with left handed equipment, in the long run he'll be a more consistent shooter. For a right handed person it's a bit awkward at first, but with practice, running a lefty gun becomes natural.
