If you already filed your income tax return, you cannot "re-file." You will have to wait until your original tax return has been fully processed and then amend it if necessary. You say your youngest child was not included for EIC. A couple of things--you can only get EIC for three children even if you have more than three kids. If your youngest was born in 2016, then you need to say she lived with you the whole year; make sure you entered her Social Security number.
If you qualified for Earned Income Credit, then TurboTax automaticaly included it in your refund. There is a table that starts on page 30 of IRS publication 596 regarding EIC and the amount you can receive for your earned income:
The amount of EIC you are receiving can be seen on your tax return:
1040EZ on line 8a
on 1040A line 42a
on 1040 line 66a
If you do need to amend your tax return:
You have to wait until your return has been fully processed, then you can prepare an amended return, called a 1040X. You cannot e-file a 1040X. It must be printed, signed and mailed to the IRS.
After you print, sign and mail your amended return—1040X— to the IRS wait about 3 weeks and then you can begin checking on it at the IRS website. Be aware that it can take at least 3-4 months for an amended return to be fully processed (or sometimes even longer.)