Thank you for your patience! The 1040X is releasing today, by the end of the day. Some users are already reporting it is available. Please be sure to log out and then back in to receive updates on TurboTax Online. Also, please see, How do I amend a 2018 return in TurboTax? for more info. Don't forget taxpayers have 3 years from the date of filing to amend.
Congrats on your new babies! Please also see, Can I claim a newborn baby?, for more info on reporting your new child in TurboTax.