1) buy a money order titled to Bank of China, buy USA$, would be easier to cash in China, costs a couple of bucks;

2) bring it to Bank of China, (branch here), they will mail it to Bank of China where your parents are, they can cash it right away once received,
costs around 20 bucks, depends how much you mail, if it's urgent, you can ask for a TT, telegraph transmit,