List<Element> children

List of the direct children of this element.

This collection can be used to add and remove elements from the document.

var item = new DivElement();
item.text = 'Something';
document.body.children.add(item) // Item is now displayed on the page.
for (var element in document.body.children) {
  element.style.background = 'red'; // Turns every child of body red.
}

Source 

List<Element> get children => new _ChildrenElementList._wrap(this);
void children=(List<Element> value)

Source 

set children(List<Element> value) {
  // Copy list first since we don't want liveness during iteration.
  var copy = value.toList();
  var children = this.children;
  children.clear();
  children.addAll(copy);
}