I highly recommend the Baby Centers in both parks...they're a nice quiet location within the parks for nursing, diaper changing, etc. Also, if you're going with other adults, I would consider using rider swap/baby swap for any attraction that has a height requirement that someone would have to miss because they have to stay outside with the baby (note that the baby will not be allowed into the queue of any attraction she is not eligible to ride - e.g., you can't take her into the line with you for a thrill ride).
In terms of the attractions, the baby can go on any ride that does not have a height requirement and on those attractions you can hold her (i.e., she can sit on your lap). In this way, DLR is the same as WDW. I went with a 9 month old (so a little older) and he really liked things like the train, Dumbo, IaSW, the carousel (both of them), the Main Street vehicles, and the parades (not an attraction). We also took him on the other FL rides (not the Tea Cups though), the Jungle Cruise, the Ferris Wheel, Ariel's Adventure, etc. We focused mostly on slow-moving attractions with lots of bright colors and things to see.