Just the though of being operated on while fully conscious gives me the shivers. The only thing I can image being scarier is when they have to do brain surgery and they wake you up halfway through while your skull is open.
I'm currently on a waiting list for a specialist at the local hospital where they can treat you under general anaesthesia. It's the only way I can be treated after my childhood experiences. unfortunately the waiting list is long. I just hope it's my turn before something starts to really hurt.
I had one treatment under GA before, about 8 years ago, and it was the first and only non-traumatic dentist experience in my life. It was such a huge difference with the 'regular' experience that I simply can't understand why dentists insist on letting people experience the torture. I think they are all secretly sadists that get off on hurting people.
I'm not trying to scare you, just make sure your kid is okay with it because it could fuck him up for life.