I will try to keep this as simple as possible. You know your dog well enough to know if she will jump and bounce all over the new baby. If you think you can bring her in on a leash and let her sniff, smell, and of lick your baby, AND you're okay with her behaving this way, then a blanket on the floor is fine. If she would NOT be able to respect YOUR desires, then start with putting the baby in a Moses basket or in the pack and play. Let the dog "meet" the baby in a manner that she can't acciedently harm the baby. You may also want to try a few "practice runs" between now and then. Whether youplan to use a blanket or pack and play, set it out in the middle of the living room floor with something intresting in the middle. Let the dog in, but DO NOT let her on/in the "baby zone".
I have an Australian ColiDor (Australian Sheepherd, Border Colie, Black Lab mix) that we got almost a year ago. (My son was 18 months.) When I started babysitting an infant I knew that he would have NO problem leaving the baby alone. He was easy to train that he could go NEAR the blanket and smell AT the baby, but he COULD NOT touch the baby or blanket in any way. My niece's dog on the other hand, (a Min. Pin.) I can't let him ANYWHERE near the baby if he's off his leash and the baby isn't in a stroller, crib, carseat, or in my arms. The two dogs have completely different personality types. The Min. Pin. would never jump on the baby on purpose. He just gets SO wond up when we let him in that it's like setting off a nuclear explosion. (ONLY no radiation, 4X as much energy displacement!) The Aust. ColiDor is so mellow that the kids bounce, jump and fall on him and he does nothing.
One other thing to consider trying; have someone walk the dog before you get home with the baby. this way she will have exhurted most of his energy and likely be much more calm and submisive (Thank you Ceasar Millan of "The Dog Whisperer") before the first introduction. Ceasar often says that dogs are better able to learn new rules/ games/ ways of living when they are first exhusted and forced into a calm submisive state.
Last but not least, as hard as it is to do, remember that your dog is just that, a DOG! She is animal, dog, breed, name, THEN family. If she can not behave or follow YOUR rules, then it may be time to either find a home that can provide the attention and desipline she needs, or istall the baby gates early, so that you can keep the dog away from your new baby. Chances are that all of it will work out fine. Just remember that she will need time to ajust to the new rules. Also remember that she is a dog and will likely make a DOG type of mistake. Don't punish her for being a dog. simply remind her what you expect through love and praise. (And an occassional treat!)
Sorry this is so long! ~J.