You are a great dad for taking him shooting, well done!!
Please take this as a suggestion, not a criticism. He may find it more comfortable to adopt a conventional two handed grip (his left hand looks loose) and cock the hammer with his left thumb rather than his right thumb. It will allow him to maintain a firmer grip with his right hand. Also, this is a good time to build good trigger discipline by making sure he takes his trigger finger out of the trigger guard between single-action shots. These things can be practiced at home during dry-fire sessions.
Here's hoping you have a shooting companion for the rest of your life.