So let me preface by stating: IANAL! I don't even pretend to be. On top of that, the wikipedia article linked seems only to summarize the laws...
17. Intentionally commits homicide
Definitely not that.
18. Intentionally inflicting injury upon another person AND if he/she causes death to the person or, by resorting to especially cruel means, causes severe injury to the person, reducing the person to utter disability
Not causing physical harm.
19. Raping a woman or has sexual intercourse with a girl under the age of 14 in any of the following circumstances:
(1) the circumstances being flagrant;
(2) raping a number of women or girls under the age of 14;
(3) raping a woman before the public in a public place;
(4) raping a woman with one or more persons in succession; or
(5) causing serious injury or death to the victim or any other serious consequences.
None of these, the parents are not raping their children.
20. Unlawfully detaining another person or unlawfully deprives the personal freedom of another person by any other means AND if he causes injury, disability or death to the victim by violence.
21. Unlawfully detaining or confines another person in order to get payment of a debt does the same in (20)
22. Where a functionary of a State organ commits any of the crimes mentioned in (20).
The parents aren't detaining their children. The buyer may be though...
23. Kidnapping another person for the purpose of extorting money or property or kidnaps another person as a hostage AND Whoever kidnaps another person for the purpose of extorting money or property or kidnaps another person as a hostage.
Parents aren't really kidnapping their own child...
24. Abducting and trafficking in a woman or child AND if the circumstances are especially serious beyond the following:
Ok. Here's where it might be tricky. According to the wikipedia article you linked, abducting AND trafficking. Parents are only trafficking their own child.
(1) being a ringleader of a gang engaged in abducting and trafficking in women and children;
Systematic conception and sale of children doesn't really seem like a gang; maybe I'm wrong.
(2) abducting and trafficking in three or more women and/or children;
Again with the word abducting. Without that, I think they could get pegged on this one...
(3) raping the woman who is abducted and trafficked in;
Nope. They don't do any raping as far as the news has reported.
(4) enticing or forcing the woman who is abducted and trafficked in to engage in prostitution, or selling such woman to any other person who would force her to engage in prostitution;
Gender specific to female, and again with the word abducted.
(5) kidnapping a woman or child by means of violence, coercion or anaesthesia for the purpose of selling the victim;
Parents didn't kidnap their own children
(6) stealing a baby or an infant for the purpose of selling the victim;
Again, not stealing...
(7) causing serious injury or death to the woman or child who is abducted and trafficked in or to her or his relatives or any other serious consequences; or
Doesn't apply
(8) selling a woman or a child out of the territory of China.
This may apply, but no specifics have been given about where the children are, where they were sold to, etc...
I feel like a broken record, but none of the items in the list seem to fit very well. Sure, you can wish the firing squad on them, but that doesn't bend the law to include them for it. (This assuming that CCP doesn't dictate their execution.) Again, IANAL and I could be wrong. Unfortunately, I doubt we'll ever learn much more about this case...