Well, I'm not a parent, but I feel a little bothered by Rodent's suggestion of making grandpa play up on how awful prison is. I say - just be honest! Sure, prison sucks, but I would hate a cutesified version of this whole "prison is bad thing." It's prison, not Sesame Street! I say just be real. Let him be exposed to life young. It'll give him interesting stories to tell when he grows up. Everyone has a unique life, afterall. Also, you have no idea how your kid is going to turn out. You could do every safe thing in the book -- he could still grow up to be a mass murderer.