Here is my great grandson Trenton two years ago, shooting a left handed flintlock. This was because this was the only rifle small enough for him at this shoot.
He is right eye dominant and right handed, and when he visited here last week on the way from Turkey to Hawaii with his father in the Air Force, we went shooting again. He wants a flintlock and so I built him one. He laid his head across the stock, as above, and I realized he was getting his face away from that left-handed flint flash like two years ago. Then I also realized that he had not shot other guns and needed to get comfortable with them. So I bought a remanufactured Daisy Red Ryder BB gun and we started with that. Now he could keep both eyes open on the target, and within a dozen or so shots was hitting plastic bottles thrown into the air. Then we went to my scoped .22 rifle and shot off sand bags at paper targets, then off-hand. After 15 or 20 shots he was comfortable and proficient. Then we went to his .45 flintlock off the bags, 35 grains of Goex 3F at paper targets, with shooting glasses and hearing protection. Now he had correct form and was comfortable.
His rifle has a Rice .45 7/8" x 36" barrel and a Chambers Deluxe Siler. It is patterned after a Frederick Zorger Lancaster and has a 13 1/2" LOP.
Here is the Daisy BB gun. It was too long for me to shoot comfortably, even though made for 10-year and older kids! It had a 13 7/8" LOP. I made a new stock with a 12 7/8" LOP and more drop at the heel. A BB gun is a good way to start kids shooting, being careful with all the safety matters.
Trenton read about mountain men in school and wanted a flintlock. So I'll make him a hunting bag and horn and mail the rifle and operator's instructions to him when he is settled in his new home.