I am very close to my 3-year-old grandson and spend at least one day a week with him. He loves his grandma - but he follows me ("gampa") around like a puppy and wants to do everything I do. “We're boys”, he says. “That's right”, I say.
I have posted elsewhere about the edict I received from his mother and father (my daughter and son-in-law) insisting I don't CCW around my grandson. I agreed to compromise by leaving my gun locked in the car when at their house, and keeping my gun on a high shelf in the closet (but available) when he is at my house.
Regardless, this is a boy who will make a "gun" out of a piece of toast. In addition, his parents have bought him nerf guns and other such toys and don't really restrict what he sees on TV - so he's getting real mixed messages.
When he is with me and is playing with some form of toy gun, I instruct him to only shoot it at bad guys. I've repeatedly told him that if he sees a gun that isn't his toy to not touch it, to leave the area, and to tell a grown-up. Then I make him repeat it back to me, which he does in the same solemn tone I used.
My point here is that no matter what the parents do or say to "shield" a child from guns, they are going to be exposed to them, and are going to be curious and interested. So the earlier a child discusses it rationally with an adult who is knowledgeable about gun safety - the safer they are going to be.
As a corollary example: We have a small in-ground swimming pool and I have taught him to never go near it without me standing by - and I do not give him the opportunity to do so. In addition, I started teaching him to swim when he was still in diapers (well, actually I removed the diapers). At three he can hold his breath, swim under water by himself, and swim to the ladder.
Knowledge = Safety - Ignorance = Danger
P.S. I have a Remington .22 semi with a scope that I can't WAIT to share with him! It will probably be a few years before he and I can whittle down his parent's attitude. I will respect their wishes because they are good parents and it is their call.