You will have to print and mail your tax return since the amendment on your son's tax return will not be processed for at least 4 months if not longer.
You can pay the federal taxes owed on the IRS payment website using Direct Pay - https://www.irs.gov/payments
In TurboTax when asked how you are going to pay the taxes owed select the option to pay by mailing a check and then do not mail a check.
