Cod, if it helps any the reason I had surgery is because I have a lazy eye. It does not make my lid droop. But, the eye was literally turning in. So I had one crossed eye. I had the suregery at 3, and it was cosmetically succeddful (though the vision is not what it is in my right eye). I have met people with a lazy (or "wandering") eye and I find it very distracting to talk to them. And it always makes me very grateful that my parents had mine fixed. I would have rather had six more surgeries than a crossed eye.
I suppose if you can try to put yourself in your DS' shoes and think right when he's 18, will he want to have an eye that doesn't droop at all or will he resent me for putting him through another surgery?