My daughter is 6 months old and it was a breeze. She was so tired she slept a lot of the time anyways in the stroller. Bring a blanket to cover up the stroller when they sleep. My wife brought plastic clips for the blanket and it worked great. Get the individual packets of formula too...
We traveled with a 15 month old as well, and the 6 month old did A LOT better than the 15 month old. Disney with a baby is a breeze!
We were surprised that children could be held on most rides-- Train in MK, Living With the Land, Pooh, Snow White, Peter Pan, the clam shells, Figment, Dumbo, Haunted Mansion. I would think it could be a terrible liability for Disney but like I said babies can be held on all of the rides except for the obvious ones!! Some attractions like Bugs Life and Muppets are too loud for babies though, but you can certainly take them in!!