You don't have to mail in your tax return. If you wait until the IRS accepts your father's amended tax return, you can e-file.
The IRS says it taxes up to 16 weeks to process an e-filed amended income tax return. You can e-file a tax return electronically through mid-October. The IRS just extended the regular filing deadline (no extension) to Monday May 17. You have time. It's up to you whether to mail it in or wait. The IRS will hold up your refund anyway until your dad amends his return.
