Hi Divamom,
Welcome to the board! While we haven't done anything as exotic as China, we did relocate from the States to Europe last summer with a
severely ADHD 14yo boy, and a mildly inattentive ADD 11yo boy. They are both really enjoying the experience of being oversees and we like living in an expat community where it is easier to make friends.
The area that is something of a problem for us is that the international school they attend is, naturally, a private school. As a result the school is not obligated in any way to make modifications for my eldest son's disability. And, I can't advocate too strongly for him because they will simply ask us to leave.
So, if your son is currently receiving accomodations, I'd say that's one thing you should consider. Otherwise, I think it is a good experience for them to see that the rest of the world lives differently than we do.