Your children do not need to apply for a work permit once they are admitted as an immigrant with their immigrant visa or have already been approved for adjustment to permanent resident status. As a legal permanent resident, your children should receive Permanent Resident Cards (commonly referred to as 'Green Cards') that will prove that they have a right to live and work in the United States permanently. If your children are now outside the United States, they will receive a passport stamp upon arrival in the United States. This stamp will prove that they are allowed to work until a Permanent Resident Card is created.

If your children are in the U.S. and have applied to adjust to permanent resident status (by filing USCIS Form I-485, Application to Register Permanent Residence or Adjust Status), they are eligible to apply for a work permit while their case is pending if they are over the age of 14. Your children should use Form I-765 to apply for a work permit.