I used to have a shih tzu who thought he was human, so he really didnt have much interest in other animals except to bark at them.
I know some people with cats & dogs though, and since your pup is so young, he'll adapt just fine. The cat might get annoyed at first because the pup may try to get rough and play with him. I'm sure in time they'll get used to each other.
My dog was great with infants, he seemed fascinated with them & would go to them if they were crying. He kept his distance from toddlers though, as they tend to poke & tried to pull his tail.
Enjoy your new shih tzu, they are great dogs!