My dog doesn't care and hasn't changed at all. My dad's dog hates other men, so I was worried that there would be a shift there, but she also hasn't changed at all. I know some people's animals do act differently, but the ones I am around on a regular basis haven't.
I don't have or like kids, but I do have some very young cousins who have seen me in the course of my transition. They also do not seem to care. They needed an explanation as to what was going on with me, and after they had that, it never came up again.