Don't worry about pit bulls and cats. I have two pit bulls and 5 cats. The cats rule, and the dogs know it. Our bigger pit bull, Alex, was adopted at 8 months old and the cats very quickly explained who was the boss. Then about 5 months later we got a very small black kitten. Alex was very gentle and careful with her. She would climb him, claw him, chew on his ears and his lips and use him as a scratching post. All he did was whimper when it hurt, then when he had enough he would just stand and walk away. He would even clean her and cuddle with her.
We always supervised them, especially at first, but he never attempted to hurt her.