Need help on how to get guests to leave a comment on a website

Hi. I've just joined this forum. Hope to get some good advice and be of help if I can. This is my client's website: www.hallsgaplakeside.com At the bottom is a comments scroller which scrolls the recent posts. Presently, my client has to post comments herself to get them to appear on the scroller. She would like to have a Leave a comment button ( text would be fine ) under this scroller which would direct guests to a page where they could leave a comment. She would like these comments to appear in the scroller. Is there a widget which might do something like this or what would be the best way to approach this?
Hope someone can help.
I'm stuck!