I have not had surgery so I will offer no advice. Your son is a strong brave little man, I wish him the very best!
You have been given advice from the best this board has to offer on nissen fundo surgery (Bill). A member named Dencha is top notch on this subject as well. If I needed advice for my own child, I would feel good in their hands.
I have two children that needed a major surgery and I can't tell you enough the importance of making sure the surgery is done at a childrens hospital. IMO, it makes a huge difference in the success of the surgery. Remember, in most cases if your not there already you can ask for a reference to one.