Long story short - you won't be able to move all money at once, due to China's policy on foreign exchange control.

I would not suggest anything beyond legal...

It is a fairly complicated and costly process.

When a customer intends to cash a foreign check/cheque, the depositing bank will need to tender the physical check/cheque to the withdrawing bank for processing.

Because of all the complications and costs, not many banks are willing to do this.

Routing number is for banks within the Federal Reserve System. SWIFT is for international banking purposes, which is a necessity for international wire transfer unless the bank can accept routing number.

The U.S. law does not prohibit currency transportation. However, all transportation above valued USD$10,000 or equivalent must be reported to CBP by FinCEN Form 105 promptly. Your customs declaration is not sufficient (if applies).

Generally, there would be no seizure when you promptly report the transportation, even in a major amount. Seizure is generally a direct result of failure to report.

His son will be an adult by the time he flies back, so he can take 9k on his own without the need to report anything.

Making a series of transactions or entries/departures below $10000 to avoid reporting is in itself a crime.

1. Pull out the 18k in a single transaction
2. Keep 9k, and give 9k to the son

How is this a crime?

See link above you quoted yourself.

And why on earth should they be taking steps to avoid reporting: what do they have to hide.

Myself, I think taking cash is a bad idea for all sorts of reasons. But if they go that bad route, just take and declare the whole amount, no funny business.

The fact they are father and son is not relevant because they are different people, and both are adults.

I believe that the biggest problem is how you can get this money away from China, not how you can get this into the U.S.

I am not sure entrusting a recent adult for this kind of money is wise.

The money is clean. So there is absolutely no reason not to report it.

But with this much of cash? Yeah...it is a bad idea.

Not true.

In this case, because the father and the son will return separately. So it should be fine.

Nevertheless - CBP uses the same customs principal in dealing with this transportation - not $10,000/person, but $10,000/travel party.

So many people confused about the USA 10 thousand dollar thing? I can travel with a million in cash if I wanted as long as I declared it and have a reasonable explanation.

People are making this a lot more complicated than it is.
1- you can carry more than $10,000 as long as you declare it.
2- Despite exchange controls (limit to convert to foreign currency is $50,000 much above the $18,000) there is no problem to wire transfer finds to US. I have several friends who do this regularly to pay for tuition for their kids in the US.
These are the two simplest options for the OP.

Because many don't actually travel in cash, but plastic.

Nevertheless - financial institutions routinely import/export currencies into/out of the U.S. So shipping millions of cash is no big deal for CBP, as soon as the money is clean and legitimate.

intent - state of mind......;)

1. Section 5324. Structuring transactions to evade reporting requirement prohibited

(3)
structure or assist in structuring, or attempt to structure or assist in structuring, any importation or exportation of monetary instruments.

There is also the slight risk that US Border Patrol may decide to confiscate your money and declare that they suspect you of some crime. The risk should be small, but with cash, there is the risk of unwarranted seizure (temporary or permanent) that would not exist in a bank transfer.

https://cimg5.ibsrv.net/gimg/www.fly...81aa65eb9b.jpg
https://cimg1.ibsrv.net/gimg/www.fly...d96f36e72a.jpg
U.S. Customs and Border Protection

If I were to give you 9k in hard cash, there is no way in hell that the US people would have a clue.

Don't forget that CBP has search authority at all ports of entry. In many cases, these incidents happen during a search.