Corgis and children "can" be a wonderful combination or it can be a disaster. As for my background, I've lived with both breeds for close to 15 years now, been involved in breeding, conformation and right now am the the rescue chair for my regional Pembroke club and also volunteer for Cardigan rescue. I get to hear and see a lot of corgis and children stories.
One of the top reasons we have corgis turned over to rescue is incidents with children. I just had a call today about a 3 year old male growling at the 17 month old daughter who has just discovered the family dogs. Of the three, this corgi is the one they are having problems with. It is for this reason that many Breeders (that is breeders w/a capital B and the ones you would want to purchase a pet from) as well as rescues do not adopt to homes with children under five or six. Having said that, I also know of a number of homes from another corgi list where the corgis assign themselves the job of nanny to babies and children. I recently had a young corgi boy, just turned a year that was originally bought as a 12 week puppy by grandparents as a gift for their six week old grandson. Life changes, baby demands left not enough time for training and devoting to the corgi. He is one that is great with children and needs them in his life. His new home has three from 12 to 5 in age range, their assorted friends and he is in bliss. So a lot just depends and with the 9 month old baby, you may be advised to wait until the baby is older before getting a corgi for your home.
My recommendation would be to go with a young dog/older puppy instead of with a baby puppy. They will be more settled, have some training in place and not so time consuming considering you also have one that will be toddling soon - two babies at the same time is a lot to handle. Another one I had come through rescue was 18 months old when she was turned over to us and her background was much like the scenario I just described. Breeders will sometimes have younger dogs or older puppies that may not have turned out for the show ring like they hoped and that can be something like - the dog just preferred being a homebody and hated to show. You will want to deal with someone who can and will give you an honest evaluation of the corgi and will match the corgi to the needs and dynamic of your home. Reputable Breeders and or rescues can and will do this.
Health concerns are primarily eye problems and hip dysplasia. Parents of puppies should have their eyes cleared by a CERF exam and a breeder will be able to show you this documentation. An additional eye concern in Cardigans is PRA (progressive retinal atrophy) for which there is now a DNA marker. Documentation as to the dog being cleared should also be provided by a breeder. Hips are x-rayed and evaluated by either OFA or PennHip and a breeder can provide documentation of the results. Even though parents may pass all tests with flying colors, there are still no guarantees as Mother Nature always has the last word. What makes a difference in Breeders is if something should happen, they will be there for you throughout whatever.
Male or female? A lot depends on the individual corgi, however I find, as do a large number of breeders across all breeds, the boys have just a little more element of sweetness to them than do the girls. They aren't quite as aloof, that you/the human might have an opinion matters to them. Corgi girls are not necessarily sugar and spice and everything nice.
Differences between the breeds - this is a new explanation a friend and I came up with this weekend. Pembrokes are more like fighter pilots/flying aces - they are a little more by the seat of their britches, on the edge thinking on the fly. Cardigans are more like bomber pilots - they figure out a course, set it, and follow through. Pembrokes rarely meet a stranger and introduce themselves; Cardigans are a little more reserved (this does NOT mean shy) and will wait to be introduced. For some more differences and research for both breeds I suggest the information which can be found at <http://www.corg-l.org> This is another good article, which parts of which could also be applied to searching for a Cardigan.
<http://ohiovalleycorgi.org/FindingaPembrokePuppy.htm>
I would also recommend your DH become involved in the research as well so if you decide a corgi is a breed for you, then you can both decide as to what might be the best timing to add one to your family.
Good luck!
Debbie