I have heard of replacing tendon release surgery with MFR. They just release the fascias instead of the achilles itself. MFR maintains the boys' ability to walk much better than tendon release and is much less invasive and difficult.
Is your son being seen by Dr. Wong? If not, you could email her about this type of procedure. I'm not sure about doing this procedure in other areas of the body.
There are clinics that do myofascial release therapy sessions. One mom takes her son to one of these places once a month in the hopes that it will help prevent contractures.