Great question. Do not ADD the child to the application or they will request medical and other stuff, plus fees. All you need to do is list them as non-accompanying dependents on the main form, then as children on the family form. Additionally, you will need to upload their birth certificates. My twin boys were born in 2020 and that's what I did. I got COPR in Jan 2023 and they never asked me anything about the babies. Just be sure to include a letter of explanation saying they are list as such because they are Canadian citizens. You will be fine.