I see that you are using the standard Twenty Ten theme. So am I. And I have complete control of exactly what Pages are in my menu, in what order, even the hierarchy of Pages.
All on the Admin panel, in Appearance-Menus, by defining my own custom menu, selecting what Pages I want to include. And using Drag and Drop to define the order and hierarchy. Quite slick actually.
Right out of the box, with no plug-ins.