I would recommend you to create linked documents (link documents from other sites if they are in the same installation of Kentico CMS
). Please see here: http://devnet.kentico.com/docs/devguide/creating_a_linked_document.htm for more information about linked documents. Then you may use standard menu web parts.
Optionally you could create empty pages and redirect them by:
document Properties -> Menu -> Menu action -> URL redirection