1) Setup 529 accounts for your son and put as much as possible. You need to save some money for your son in case something happened to your income.
2) Put as much as allowed to your 401K (or IRA) account.
3) Buy an apartment in China under your name.
4) Take luxury trips, bring your son along.
Anybody can spend money!!!
5) Write a will and make sure your son is provided.
6) Separate accounts. Negotiate on who pays what for the family. The daughter's tuition should be paid by her father or herself.
7) Tell your hu*****and that you don't want to control him, so you are not going to spend your money on his hobby or his daughter, which will make him feel bad.
Be honest with you, I think one should provide for spouse's kids; except, when the party does not appreciate your effort and take it for granted, then forget about it.