First off I had a wonderful cat that I supidly never brought around any children, when I was pregnant the cat got jealous, and when my preemie baby came home she started to urinate in the crib and on the baby clothes and we NEVER had a problem with our cat ever before. Well the baby came before the cat so guess what we found a new home for the cat.
Then:
I got a adult female cat from the Humane Society when my daughter was about two years old and things went horribly bad.The cat HATED my daughter. I have always said if I got a another cat it would be a kitten so I could train and get the kitten used to children.
My daughter is 5 now and just started within the last few weeks being nice to animals. She never purposely was mean but out of her maturity and intelligence just didn't know and comprehend how to be nice to kitty's. She would hug them and at the same time almost be choking them. We do have a ferret and my daughter trys so hard to be loving but at the same time she is to rough. I have to babysit their interaction constantly or put the ferret in a cage.
I personally think animals are better for older children. But if you've got the time and patience to babysit your child and the cat together every second go for it. I recommend a mellow kitten.