Since the views allow you to define functions, you I would expect you can use a recursive call to display the child items (warning the following code has never seen a python interpreter):
define a function:
{{def showtree(tree):}}
<ul>
{{for i in tree.items:}}
<li>
Displaying child {{=i}}
{{showtree(i)}}
</div>
{{pass}}
</ul>
{{return}}
usage:
{{showtree(mytree)}}

