I have AFD and I'm 24 years old, I run a mile three mornings a week, I rollerblade, bike, swim, and babysit my 2 & 4 year old God-children (the mothers here will realize that can be an athletic event in itself). Not to brag but I graduated in the top 10% of my high school class and graduated college with high honors. The point is, I have a healthy, happy life despite the AFD.
When I was younger I was prone to dizziness and/or fainting spells from intermittent rhythm problems and the mixing of oxygenated and unoxygenated blood, and I had & still have a heart murmur. As I got older the AFD closed to some degree but not completely; I sometimes get dizzy or light-headed for a few seconds if I over-exert myself and I get PACs fairly frequently but other than that I don't have any clinicallly significant problems to speak of.
Now, since I have AFD and a resulting heart murmur I need antibiotics before surgeries or dental work because I am at an increased risk for endocarditis (an infection in the heart). There's also the risk of atrial tachycardia, atrial fibulation, and/or blood clots.
On the flip side, surgery could close the AFD but it is also not without it's own set of risks. Blood clots from the heart-lung bypass machine, problems with the anesthesia, scar tissue in the heart from the surgery causing PACs, and the need for antibiotics before dental work or surgery because of the increased infection risk.
Basically you need to talk to your doctor about the benefits vs. risks regarding your child's specific symptoms. Realize that 'fixing' a heart defect with surgery still makes one a chronic heart patient. And, speaking from experience, kids understand more than we give them credit for so be sure to explain the options, risks, and benefits to your child and get his thoughts on the subject. After all, he is the one who ultimately has to live with it.
Just my two cents and as this is my very first post here I hope I haven't intruded