CSHARP

unity get all children

foreach (Transform child in parent) {
  //Your code
}

unity get list of children

List<Transform> children = new List<Transform>(transform.GetComponentsInChildren<Transform>());
//!!!!DISCLAMER!!!! This will also include the parent object for whatever reason.
//Heres a less elegant solution that wont include parent:
List<Transform> children = new List<Transform>();
foreach (Transform tr in transform) children.Add(tr);