I’m surprised TurboTax allowed you to print a tax return with a blank Social Security number for one of your dependents. If you claimed the child on your return, that will be enough reason for the IRS to issue the ITIN. TurboTax should also not have given you the $2000 child tax credit for a dependent without an SSN, although it may have given you the $500 credit for a “other dependent.” In that case, no financial adjustments would be needed when the ITIN is issued and the return is processed.
However, I am not quite understanding your statement. If you prepared a tax return and you listed child #1 who had a Social Security number, and you did not list child #2 as a dependent because they had no Social Security number, but you included a W7 application for child #2, the IRS may indeed send that back to you for correction. But it is not clear to me from your statements exactly what you did.
