Applying Citizenship (for ILR status) with my children's expired BRP and passport?

Hello,

We're(me,spouse & 2 children) holding ILR since 2014, and planning to apply Citizenship with my two children. But, my both children's BRP and passport have been expired. Their BRP expired on July 2019, and Passport expired on October 2018. (We had planned to apply the citizenship on last September, but couldn't go ahead as we faced some financial issues, so we had to postpone the application). So, Now I decided to apply citizenship for myself with my two children.

My questions are;
1) Can I add my children with my application with their expired BRP & passport?
2) Or do I need to get my children's BRP renewed first, and then to apply the citizenship?
3) My spouse is not applying this time with us due to the higher fee for all of us at the same time, so we planned to apply the spouse's one on a later date. Is our decision OK? or Do we need to find the way to apply together at the same time?

Thanks in advance for your valuable time and inputs/feedback/advice for my questions. Many thanks.

ILR status does not expire. You can apply with expired BRP and passport. Your spouse can apply later