Unless he smokes while he reloads, reloading is way safer than cooking. Nothing hot, nothing sharp, nothing electrical. If he can handle a gun safely, he can reload safely. My 6 year old would sit on my lap and pull the handle. Modern powders are safer than hollywood would have you believe, and there are plenty of books to teach you.
Unless you're casting lead bullets as well. You wouldn't get me anywhere near lead vapor.
Thanks.