Got the following after emailing the said email:
" Thank you for contacting Qantas.
This inbox is dedicated to customers who hold a Classic Flight Reward booking on a partner airline flight, which has been cancelled or had a schedule change.
Please ensure your query includes your Booking Reference. Queries will be prioritised by the date of travel.
Enquiries on other issues that are sent to this inbox will not be actioned or forwarded on.
Please refer to
https://www.qantas.com/au/en/support/contact-us.html for the best way to contact us for other enquiries.
Contact us | Qantas
Find out how to contact us to change your booking, call your local Qantas Office, contact us in Australia on 13 13 13, search our FAQs, provide feedback and more."
Not sure if they have moved to another email address ?
TLDR : Managed to create e-tickets for my infant after speaking to CS over the phone. However, I can't select the bassinet seat as the new booking contains only my infant (tagged to my wife). In the main booking there's no infant so I cant select a bassinet for my newly added infant. Was advised to request at check-in counter but chances are slim...