Hello, I am on L1 in Texas, my wife and kid are on L2 and not working. Do I need to get ITIN or SSN for my wife?
Can I obtain ITIN for my son before I file my tax?

You will attach W7 (ITIN application) with your tax return.

Agreed.

Unless you have an over-riding need for the ITIN (for example, to register your child for school or to allow your wife to get a bank account), the IRS generally will NOT issue ITINs unless the W-7 is submitted with the annual tax return.