We went in October 04 with our 8 month old son and had a great time. The key for us was planning. Realizing that this would be a much different experience than our previous 3 trips that were go, go, go. We had a nice breakfast by the pool of our resort, WL, every morning followed by a long walk (baby in stroller of course). We would then go to one of the parks for a few hours and return for some quite time by the pool and a nap (our sone was not a good stoller napper). Dinners were planned early so our son could be in bed by 8 - 8:30.
A quick list to consider:
Know where the baby care ceters are in each park before you go. They are cool and quiet areas to feed and change your child and escape the heat. We were impressed at how clean they were.
Schedule your time on paper...I know it's vacation but it worked well for us. Pre-baby we always got caught up in the attractions and rides and spent long tiring days at the parks, something we could not do with our son.
Take along one of those fanny-pack sized insulated bags and keep an emergency supply of water and snacks in it with a couple of wash cloths. The parks can get hot fast and you don't want to wait in a line if you notice that your child needs to cool off fast.
Pack lots of extra's if you have the space. Food, diapers, and, toys. There all available at Disney but cost a lot more.
Consider renting a car, it allows for a quick get away from the park if you need it. It cuts down on your travel time to and from the parks. Also, it's much, much faster to get from one resort to another for dinner.
Understand that most rides will be off limits to your child for safety reasons. Our son still had a great time taking in the sites.
Have a great Disney and family experience.