I am in almost the same boat as you. My son is four and I am still unsure which way he will shoot. I am a lefty and think he may be also. I do two things to try and get him ready. 1. I gave him an old scope and have him throw it up to his eye once and a while. 2. I bought a 24" blowgun and just use the plastic part of the dart. We shoot 2 liter Pepsi bottles at about 10-15 feet. I am not concerened which eye he is using because he seems to hit the bottle almost every time. When it is time and I hand him a rifle, I think he will automatically sholder it which ever way feels best. Good luck.