Your son sounds bright and creative! Here arr some things you might try: Get some puppets and role play the situations. Make the the puppets ‘talk’. Have him be the one who is interrupted, and the one interrupting. Talk through how that feels. Come up with a cue word or hand signal to remind him when he is interrupting. Let him choose the cue. Get a kitchen timer, and have him practice playing independently while the adults talk. Start with a very short amount of time, such as 30 seconds, and gradually build up. Use incentives if you think it will help. Good luck!