Applying for british citizenship for a 15years old with ILR born outside uk with ILR parents

Good morning
We want to apply first for our son, 15 years old and that for our daughter, 11 years old to get the British citizenship. We moved in England in 2018 , we all have ILR for 2 years now as we applied for it after 5 years of living here, but none of us is British. My son was born outside UK. The parents won`t apply yet ,for the British citizenship , but my son`s future will be here, in UK and will be much easier for him having this
I now we need to apply under the MN1 formular . Except of filling this online, what other documents do we need to prepare so that the application to be successful.
Also , will there be any reason for the application to be refused?
Thank you for your answers

The MN1 guidance has a section listing documents required >> https://www.gov.uk/government/publicati ... 1-guidance
Don't see any reasons why the applications should fail.