How can the father of the children issue a power of attorney so that the child is released abroad?

A child under the age of 16 has the right to leave Ukraine accompanied by a parent, grandmother, grandfather, adult brother, sister, stepmother, stepfather, or other persons authorized by one of the parents in a written statement certified by the guardianship authority , is carried out without the notarized consent of the second parent and in the presence of a passport of a citizen of Ukraine or a birth certificate of a child (in the absence of a passport of a citizen of Ukraine)/documents containing personal information.

Therefore, the child's father needs to write a statement authorizing another person to accompany the child abroad, having verified it at the guardianship and guardianship authorities.