protecting some content for booked clients

Site URL: http://www.buildabettermousetrip.com

I have a site www.buildabettermousetrip.com for our Disney Focused travel agency.  The majority of the site is fashioned after a typical "fan site" but I need to be able to put up content that is specifically for clients that book our services.  How do we secure a section of the site as if someone subscribed to us, as is generally used on sites all over the place?