Inverspark

Hi , Just wondering if anyone has had this issue before and where i stand.

Been living in Nz now for just over 5 years.
Wife and 2 children.

Things between us have gne tits up and looks like she will move back to the uk.

She would be taking the children with her and i would like them to have at least been granted citizenship before they go.

Just wondering if they can be granted citizenship whilst they are not here?
They have lived here the full 5 years and due to them not being citizens i cant keep them over here.\

I just want them to have the choice to come back if should they wish to.

Any info would be great

regards

David