Your first step to shutting off a sub event is to select "Subb event Shutoff" in the advanced features tap. Once you check that box, it will populate on the left side bar.
Now, once you click the new tab on the left, you will be allowed to shutoff any of your subevents.
Once you shutoff the appropriate subevent, you have the option to keep it visible, or to hide it on the registration page.
Remember to SAVE all changes before leaving the page.