My kids each got their first gun at the age of 4. This was against my wishes at first, but then I thought that the earlier they knew what it was, the better off they would be. My husband was a Sheriff Deputy, so he taught our son the parts of a gun every day when he got home from work.
From the time my husband got hired as a Deputy, I firmly put my foot down (because our son was only 1 then), and told all family member that NO toy guns (even BB guns) were to be bought for our kids. It's too easy for kids that have real guns and toy guns to forget and point a real gun at someone. Yes, the kids are taught to NEVER point a gun (real or toy) at anything you don't intend to shoot, but accidents and forgetfullness can still happen. My MIL has since bought my son a BB gun, which did NOT go over well. My kids are also no allowed to go hunting with just anyone, including my MIL or her husband or my BIL. I just don't trust them enough to not get my kids shot. Boy did it PO my MIL when we told her that they weren't allowed to hunt with her, but could with my FIL. At least I can trust him to keep his eyes on the kids while they are out.