At mealtime, sit at a certain distance from him. With the plate and utensils of your child’s favorite hero, which you will buy, start eating, making sounds that show how delicious the food is.
At no point speak to him. Coordinate with your wife to sit beside you. Eat together, laughing and showing that eating is enjoyable; make him want to join in.
When he shows interest, create a small obstacle as a condition: tell him he would need a plate just like yours to participate. Then, let him know you just remembered there’s another one like it in the kitchen. Allow him to join you and your wife.
This should work. Try it and let me know afterward.