In terms of space, all of the rooms at Port Orleans seem to be the same size, although the only section that officially allows 5 people in a room is the Bayou section, which has trundle beds. My guess is that Disney uses this to get more people in the Bayou - My preference is certainly for the French Quarter, or the Mansions. So anywhere are Port Orleans should be fine with the baby.
The Contemporary and Poly also allow 5 people in the standard rooms, since they are larger than most other standard rooms on property.
We've also stayed at the Family Suites, and the upside was the small kitchen. Having 2 TVs was also helpful, for someone who gets tired of the Disney Channel, as was the extra space, much more than in a standard room. And 2 bathrooms.
Please let me know if I got any details wrong. It might help us on our next trip.
Mick