How to add an external file edit access for clients

A common feature of websites I build is that clients have lists of testimonials and quotes they want in their websites. I use a javascript include which chooses the quotes randomly from an external file in the root and places them in the website pages. See this example: http://www.gwendolinelamour.com and note the testimonials in the ‘quote’ panel at the foot of each page. Refresh the page and you’ll see it has changed.

The testimonials are listed in an external file which the client cannot edit unless they are familiar with js and css coding and ftp access. I would like my clients to be able to edit their testimonials via the WP dashboard but I have not found a plugin which enables this. Anyone suggestions?

Thanks
Tim, London