I believe you would need the Open Hours plugin developer to either
a.) add that to the code, so send him the link to the documentation
or
b.)tell you where to put it inside their code.
I don't know how the plugin works but if it outputs to one page, you could exclude the path from caching on the caching page. (example: tell it not to cache /open-hours if the url you found them at was http://www.francesco.com/open-hours
tim