I'm not sure if we should wait till our youngest is older? He's just three.
He's also a bit violent to humans, though he adores cats and follows them around the neighbourhood. He has always been gentle towards any that have hung around for long enough to find out 
I don't know if we ought to wait. I know some rescues don't allow adoption till a child is five or so, anyway.
We also have to find somewhere for a cat flap.
Any thoughts appreciated - we're on a quiet road, everyone has a cat except for us, we have our own garden, and we are upstairs though we have a fire escape at the back.