Livy do I need to come out there and help you? LOL Just do it a little bit at a time make sure you have someone handling Gracie while you handle the baby. Let her sniff the baby in your arms and get aquatinted with him a little bit each and every day until she get's used to the baby. You will be surprised these dog's are really smart and they know a small child from an adult a lot of the time. I have watched mine interact with kids and they have always been a lot gentler with kids than they are me LOL.
Look me introducing Karma with my sister's 3 month old baby .. Don't be afraid just take it slow