If you don't live somewhere with your own land, what is the point of owning a gun?
It's illegal to shoot over land boundaries, it's illegal to own one that's over a certain pressure (you need a firearms cert if it's over and they're a pain in the arse), gun cabinets cost a bomb. There's a reason they keep guns in the country; because they're used to all the shit that goes with keeping guns.
Then: what are you going to shoot? If you aren't on a farm, how much vermin can you possibly find? You aren't allowed to shoot crows or rats unless they're on your own land (plus there's the risk that the pellet will cross land boundaries). Shoot a can, you say? Well, you can, if you've got a big enough garden and you're sure that the pellet isn't going to go outside of your garden.
Having a gun at home, with kids, and no cabinet, is asking for bloody trouble. Accidents can happen - animals and children can get injured or killed. Can you be sure they haven't got ammunition? That they won't shoot it without adult supervision? Other posters on here have already said that they have guns, in locked cabinets with the keys scrupulously hidden.
Sounds like a royal pain in the arse to me. The OP's husband should have bought membership to the gun club, not a gun. You can shoot what you like there without any of the hassle.