Well, ideally, you guys would be checking your website code into a revision control system like Subversion or Git or the like, and you could just instantly pull any version or branch of your code into any directory you like
You’re likely to move a lot of things you don’t intend on moving (including the “domains” directory, and any user home directories, breaking email for all of them).
Is everything you’re modifying for the website in the public_html directory?
You could always just move public_html around rather than it’s entire parent directory.
So something like:
Make full backups of your entire server! But this step is unnecessary, because you’re already doing all that, right?