My son was born with a Congenital Diaphragmatic Hernia (big phrase for a hole in his diaphragm). He had surgery when he was just 30 hours old. He doesn't remember any of it of course, but he was left with a 6 inch scar across his abdomen. When he was just a baby I started telling him that that was where the doctors put his super powers. Now he is proud to show off his scar...it makes him special! Anywhere we go if someone asks to see his super powers, up goes his shirt. If you ask him where they came from, he will tell you the doctors gave them to him. If you ask him what he wants to do when he grows up, he says he wants to fix the babies. He's only 4! Tell people as little or as much as you are in the mood to tell them. When I have the time, I explain to people what CDH is, because like me before having Dean, most people have never heard of it. I think the education can do them some good. Many babies die from CDH, Dean and I were VERY lucky that he is as healthy as he is today. For that reason, I don't mind explaining to people what we went through when he was born. At the same time, if I'm not in the mood to get into it, I will simply say he had some surgery when he was a baby and he's fine now and then I will change the subject. It really is a personal decision what you choose to share with other people. The most important thing is what you tell your son now and later as he's get old enough to understand more.
Good luck to your family, I hope things continue to improve and your son continues to thrive!
K.