sounds like they would be worth the time. just tell them you dont want the guns around if your not around . i think they will listen to you -they wouldnt want to jepordize your friendship(fishing,ponys etc.) you may be the only role model they have!! tell them if they help you do chores(whatever) you seem like a pretty cool fella -figure something out that they can earn as a reward(whatever) i got a feeling they may respond to that
ask if they had any safety courses- if not i guess its up to ALL of us to make our hunting safe, as i said i think God delivered them to you for a reason.
teach em well