I'll second what rj said, and my kids are half Chinese.
There's a lot of "go speak English to the foreign kid" pressure from the parents too, which makes their children reluctant to even approach our children because of course no one likes to be put on the spot. And the ridiculous thing is my kids don't even really speak English, Chinese is far and away their first language.
Standoffishness isn't the problem it is if anything it is that they (the Chinese kids and especially the parents) are overly conscious of the fact that the kids are different. Kids really don't like having their differences pointed out and made into an issue. RJ's kid is too young to really understand what is going on but my son will be 4 this year and he is definitely starting to get it and doesn't appreciate the attention.
As for 3rd culture kids, I only really know half-Chinese half-foreign families who have stayed in China for the long haul, but those aren't 3rd culture kids, they're 2nd culture kids. Expat kids here in China do tend to be of the expat package variety, staying here for 2-3 years and then their parents are on to the next post -- France or Dubai or Vietnam. Of the 2nd culture kids I know one in particular grew up here, attended the public school system here (in Kunming) and now is in his first year of university in the States (attending his father's alma mater). He's really struggling because although his spoken English is reasonably fluent his writing skills are really lacking. I don't know if they had it to do over if they'd have stayed in China or not -- they're the directors of a study abroad program for American college students and both very happy with their jobs -- but I think for my family we'll be moving to the States at some point in part so we can avoid putting our kids in Chinese public schools.