Wordpress function.php IF statement

I have function in my [login to view URL] that adds class to body (disablesidebar) if the woocommerce category has a child category. In addition I have function that unregister specific widget globaly. What I want to achive is to combine those two function so that the widget remains unregistered until the category has no child category. Background. I use Woof filter wich is quite resource hungry. Since I show products only on the last category child there is no need for filter before and would speed up the site if filter loads only when needed - when products are shown.