Hi!
I went to the Magic Kingdom with my son when he was 4 months old. He was the type of baby who did not like his stroller very much so there were some challenges with keeping him content. Remember a hat with a brim, sunscreen, wash cloth in baggy that you can wet in a drinking fountain to swab him off if he's hot and sticky, and some sort of stroller shade for the intense sun.
There is a wonderful baby care station that has a dark, quiet nursing/bottle feeding room with rocking chairs, as well as rooms with changing tables, high chairs and a kitchen for warming bottles/food.
There are many attractions that he can go on with you and sit on your lap. My son LOVED It's a Small World, looking in awe at all the colors and movement.
Sure, Disney with an infant presents some challenges, and of course he won't remember going, but you can make some wonderful memories together. It would be cool to take lots of photos with double prints. Save one set to add to photos of later trips you might take and make a "Disney-Now and Then" scrapbook!
I'm sure you'll have fun if you are well-prepared and flexible-good luck!