I'm no pro,but folks seem to enjoy my little cat tales.
I suggest first off try a couple of short storys to develop a style. Mine is to think of a situation and write as if I were the cat in that situation.
You really have to target age groups with kids as it affects how you write the story. Younger kids read a simpler style than older ones and don't follow complex plot lines. One of the most memorable cat storys I remember was titled Jennie;but it was far too intense for younger readers.
Don't worry about punctuation,etc. You can go back and edit that when you're done. Just write the way YOU think it should be told. You'll know when you're "in the groove" because it will just flow. Cats are a constant source of inspiration.
Above all,have FUN with it. If you enjoy your piece so will your readers. Don't "talk down" to your reader group if you're angry about something or get overly "weepy" if you're down.
Meme has a couple of my storys on her website so have a look there if you like.