Definatley go with a bully breed, I've got a staffy who was a sheep dog at one point beleive it or not. I've also got a female APBT thats white with blue markings, they are both very good with my young children and the male is quite protective over them. I also kept a puppy from their litter, they're like one big happy family out in the back yard. I've never seen human directed aggression out of either one of them, but dont think for one second they would let a stranger in the house if I wasnt here. If you do get a bully just make sure it is well socialized and try not to chain him if you don't have to.