How does a girl-9 and a boy-8 from an absent non/jewish non/converted mother convert to Judaism. She went to the mikvah and he had a proper Bris Milah.
The procedure for conversion of a child (beneath the age of bar/bas mitzvah) is milah (for a boy) and mikvah, which must be done under the auspices of a beis din. After reaching the age of bar/bas mitzvah, beis din will offer the child the choice of continuing his path of Judaism, or returning to being a non-Jew. The child’s father has similar jurisdiction to beis din over his children, and (provided there is a father) he makes the initial decision on behalf of his children.
In any case, you should contact your local rabbinic beis din, who will instruct you further.
Sources: See Shulchan Aruch and commentaries, Yoreh De’ah 268:7.