I called Brent Council. They were very helpful and confirmed we could submit combined MN1 and Passport application. After I booked an appt for my kid's application, they sent out a Passport form by post, and also mentioned we could get the Passport form from a post office instead if the mail doesn't reach on time etc.
You will need to submit:
Child's full birth certificate (listing both parents' names),
Child's current BRP,
Both Parent's Passport + BRP (as appropriate)
Parents' Marriage Certificate
Child's Photo should be same for MN1 and Passport form (1+2)
I have not yet applied for my daughter (the appt is next week) so haven't delved into the forms etc yet. I suggest you call your closest council that handles combined applications. You may have to wait a while on the phone but you can clarify all your questions.
Link for Brent Council:
https://www.brent.gov.uk/your-community ... ng-service
Phone: on 020 8937 1010