Unless the required advancement is huge, distraction osteogenesis is pointless. You still have to cut bone, and double the operations - put distractors in, take them out vs one-time jaw surgery. I would simply wait till your son stops growing (18, 19). 12 months in braces, surgery, 6 more moths in braces, done.
I don't agree with this entirely.
The first part yes. IMDO looks all well and good but the simple fact is you're replacing a one-off operation with two, plus the pain of making the advancements between those operations.
As for the second one about waiting until he stops growing I do disagree. OP appears to be focused purely on operations, but what about asking why all this has happened? It seems to me that it's most logical to at least ensure there are breathing techniques, good oral posture and all that in place prior to any operation. Things we know for a fact cause facial deformities. If Dr Mew's results are anything to go by then this alone could make a significant difference for the child. What good would an operation be at his age if his face continues to grow without the tongue in the right place to prevent vertical growth? Or why advance a mandible if he will continue to breath through his mouth only to have it recess once more as he gets older?
I would at the very least take this preventative approach first to see how much it could benefit him. There's a very good chance - especially at his age - that he could avoid surgery entirely. It could dramatically alter his facial development going forward to the point where the results are better than surgery - particularly when combined with chewing harder gums to encourage bone growth. This isn't hyperbole either. The simplest example of this would be the infraorbital rims. Jaw surgery will advance the jaws and fix the bite, but the aftermath of the poor habits which led to the need for surgery often leave people with a flat or recessed midface (week cheekbones and under eye support). If he could develop as nature intended he'd have a much more balanced appearance.
Finally, if after pursuing this route you find surgery is still a necessity then by all means consult with Dr Coceanig. His results seem decent enough. That said, the best maxillofacial surgeons in Australia appear to be working in Melbourne out of MOFS (Andrew Heggie, for example).
----
Probably not the kind of response you were looking for but I hope you find it helpful nonetheless.