How to clone menus in Drupal?
If you want to be professional, use  Menu clone module all right. Simply do it on development copy of client's site.

It's never a good idea to use beta modules on production site without testing them on devel and stage, but if you do test and they work for your particular site, it's usually safe*. And if all you need are cloned menus, you can use it and then uninstall before stage -> production migration so it will never even appear on your production server.



* As safe as your tests were good.