Where were they born?
If they were born in the UK, you can register them as British citizens directly after you get ILR.
If they were born outside the UK, they can register when at least one parent has or is applying for British citizenship AND the other parent and the child BOTH have ILR. They will also be eligible for ILR only with the other parent. So, what is the UK immigration status of the other parent?
EDIT:
CR001, what can one say? Great minds...
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.