You are a kid, have fun as much as you can but don't drive your mommy to the edge of sanity. She doesn't want to hire a babysitter, nanny or some mom-helper.
If your mother has newborn baby, then you should help her as a mom's helper. Your mom will be amazed and love you more if you help her with laundry, cooking, cleaning or other household chores. As you are too young so laundry and house cleaning is enough so far. Often times, you are not quite full-fledged in helping state, don't worry, tell your mom that you will get it done soon. Don't put buttons on your mom when she has new born baby.
Just as mom takes care of the babies, it's time for the babies to care of mom too. Your mom will be happy if you strike back from creating a mess and be a good little helper. It's a wonderful adventure for kids! And anyway, Live it up and make your mommy proud of you.