i am the same way i am also left eye dom. but i still shot right hand and do great just need to adjust the sights. Also means the zero is differnt for him then anyone else. Atleast thats what i was told. When we had a AR15 my dad would shoot it would be off to the left or right can not remeber. Then he would zero it in i would shoot and it would be off. We would switch back and fourth untill the pro shop checked my eyes when i bought my bow

Simple solution, shoot with both eyes open as you should anyway...

If he's right handed and left eye dominant, both eyes open will cause his left eye to want to look through the sight and result in a focus problem. I would agree with having him try to shoot left handed. My son is left handed and right eye dominant had taught himself to shoot right handed. He's old enough now that when he picked up a bow this year, it came naturally to him.