In an interesting way this is a good example. It is indeed up to parents on a ranch to decide when their children are ready to see animals mate. It's another matter all together to decide when the small children or teens are ready to see humans mate. Either way that needs to be up to the parent or legal guardian. That is already their job.
You think ranch owners are hiding their farm practices from their children? Nah I don't believe that for one second. Ive watched 10 year olds of the most prudish family I ever known holding piglets so their dad can castrate them. Hell 20 year old Amish people can't even hold hands but will have kids help artificially inseminate cows.