Applying for Childs Passport

I was grandted ILR in early January, welcome our son later that month. I'm going through and applying for his British passport (as I understand I can do) but coming up against the following information request

Parents’ documents
For 1 of your parents, send 1 of the following:

full birth or adoption certificate - can provide, no issues
naturalisation or registration certificate - I dont have this, not even sure what it is
the non-British passport they had when you were born showing indefinite leave to remain - have passport (USA), and my ILR BRP but do not have anything literally in my passport indicating ILR, would I send both?

Grandparents’ documents - i cant send/dont have originals for any of these
Send all of the following for both maternal grandparents:

full birth or adoption certificate
grandfather’s marriage certificate to your grandmother (if this applies)

And all of the following for both paternal grandparents:

full birth or adoption certificate
grandfather’s marriage certificate to your grandmother (if this applies)

I just clicked 'first child passport' and went through the gov.uk steps. Am I missing something or should I have selected another pathway? Also, how long do they hang on to my USA passport once sent in? I travel frequently for work so need to game plan how this is done. Any advice would be appreciated. Thank you.

I did some more searching and found this post: british-citizenship/newborn-british-pas ... 83283.html

basically it would appear the online form is not accurate to those applying via ILR.

I'll fill out the form appropriately (enter all information as known, but note I cant provide originals of the grandparents information) and send in and his birth certificate, my usa passport and ILR card which should qualify/allow for processing.