Another solution would be to create pages that redirect to the hidden pages and set these redirect pages up to only allow viewing by Administrators. It would work something like this:
Create hidden page, with url '~/hidden-page.aspx'.
On Hidden Page, Remove "Include In Menu" check-mark.
Create redirect page, with url 'http://www.yourdomain.com/hidden-page.aspx'.
On Redirect Page, set 'Roles that can view this page' to Administrators.
Now, when a regular user is logged in, they will not see the item in the menu but will be able to see the page. When an Administrator is logged in, they will see the Redirect Page in the menu. You can name the Redirect Page the same as the actual, hidden page because the URL will be a full URL, not relative. I do suggest that you name it slightly different so no one gets the two confused when making changes to the settings on the pages.
Hope this helps,