My daughter, now 16, was born with a club foot. Casting did not work. She had surgery at 4 months, and complications afterwards. She wore orthopedic shoes for years. She would not wear the metal bar in between, so we gave up.
She wears a lift in her shoe on the side with the club foot as that leg is shorter (shorter tibia, smaller calf muscle are part of the syndrome). She runs cross country and is on her high school track team. She has also played a lot of soccer. She does have problems with her ankle, mainly pain, but deals with it, and the orthopedist says its OK for her to run. That's good, since she loves it!
If I remember correctly, Kristi Yamaguchi had a club foot, also.
My daughter had a club foot only on one side, which must be easier than having both legs involved like your son, but as you can see, as she grew, it became less of an important feature in her life, and she certainly is not letting it define her.
Good luck to you and your son.