you should also teach the 4 year old not to mess with them. Don't trust yourself to be perfect every time, and it's never too early to teach a young one gun safety, before his/her friends or TV does.
Oh, we do. That's been a thread on it's own before. But 4-5 year olds don't always do what they're told and there is a fine line between being safe and having an inaccessible gun.