CSHARP

unity delete all children

 foreach (Transform child in transform) {
     Destroy(child.gameObject);
 }

unity destroy all children

while (transform.childCount > 0) {
    DestroyImmediate(transform.GetChild(0).gameObject);
}

Unity Destroy All Children

void Update()
    {
    //put in any gameobject having children and enter playmode
        foreach (Transform child in transform)
        {
            Destroy(child.gameObject);
        }
    }