Parents CAN only edit Page 3 - Applicant's information.
Parents CANNOT edit Page 2 - Preferred Choices.
For Page 1 - Child's Particulars:
If your original submission indicates that the child is unborn, then you can update the child’s information while transitioning from an unborn child to a born child. After that, you cannot edit the child's information.
If your original submission indicates that the child is born, then you cannot update it. Any further updates will need to be made by contacting the support center for assistance.