While that is a lot of money for your son, $Billions are wire-transferred daily. The easiest and safest way to accomplish this is to have whoever controls the account in China ask at the bank holding the funds what information it will require for a wire transfer and what its fees will be. Chances are that the cost is reasonable and the information will involve his name, address, a phone number, ABA routing number and account number. Most wires can be sent for payment immediately, in 4 hours or as long as 2 days. Unless he needs the money immediately, there is no reason to pay for expedited service.
Make certain that your son obtains the backup paperwork (that can be mailed/emailed) showing that this was part of your wife's estate and is a bequest. That may have tax implications for him down the road and it is best not to have to scramble for documents located in China should the need arise.