You need to manually loop through the nodes and show/hide the ones you want. To hide all nodes except for the root, do this.
foreach (TreeListNode aNode in YourTreeListView.Nodes)
foreach (TreeListNode aNode2 in aNode.Nodes)
aNode2.CheckBoxVisible = false;
Assuming there is only one level of children. To only show the Children do this.
foreach (TreeListNode aNode in YourTreeListView.Nodes)
aNode.CheckBoxVisible = false;
Thanks,
HH