Way to go Starbucks!
When my wife and I got married, she tried to do the whole "the kids are not playing with (toy) guns" thing and I let it pass for a short while and told her to see what happens. She did everything in her power to throw the little guns away that come with action figures, etc... Boys just gravitate to them by making guns out of legos, etc.. I took over from there teaching them about gun safety. It is important as you are not always going to be with them every minute of the day. I hope that when they are at a friends house, and there is a gun lying around, they are smart enough not to touch it and walk away.
A proper lock box, such as a safe, are perfect for keeping guns in. There is no way that your child can get in them if YOU took the proper steps to secure the box before you walked out of the house! remember, guns don't kill people, people kill people!
A coworker lost her son to having a gun in the home. Even with a gun lock on the gun and having it locked in a cabinet, bullets locked in another cabinet. This child still got all the keys he needed and shot himself. Just because it is all locked up, never assume it is safe. 
Sounds like the gun was safe, her son was not.
