I will second what others have said.
We went down when my son was 5 months old. I made sure to bring diapers, swimmies, wipes, formula, etc from home. I did purchase his baby food when we got down there, as they were not available in plastic bottles, as some are now, only glass. This will, also, serve as extra room for souvie's from your trip!!
I brought my baby bjorn with me and when we brought my son on rides, I would put him in that. He went on small world, haunted mansion, etc.
Bring your own stroller. They are comfy in it and the disney ones are not infant appropriate (at least I don't think so).
We were at CSR when he was this age and the stroller was great to have for walking around the large resort, as well.
Take plenty of pictures, esp if it is their first trip. I take tons of pics anyways, but one of my all time favs is of just me and my son in front of cindys castle. Hubby decided to rest that day and my grandparents came over to visit and go w/us to WDW, so it was a great trip w/my grandparents (and their last trip there).