FLR(FP) based on child on 7 years route (help needed)

Hello everyone,

My family and I got our fee waiver last Monday and we filled and submitted our FLR(FP) based on child on 7 years route online. We have booked a date for biometrics and presenting documents for next week.

I need help knowing all documents needed.
1. Parent are overstayed, one has an expired passport and the other has their passport with the home office.
- Will that be a problem?

2. For the 9years old child on which basis we are applying what documents of his needs providing?

3. What other documents will help with the application.

The children (2 of them), we're born in the UK and have never traveled out.