Hi Veronica,
My daughter's first trip to Walt Disney World when she was seven months old. It is truly magical to see Walt Disney World through a baby's eyes. There are a few items I suggest packing when bringing a baby to Walt Disney World.
Since you are coming in July, you'll want to bring lots of cool, light-colored clothes for the baby to keep him comfortable. Also, bring sunscreen and a hat for him. We brought a stroller as well as a baby carrier that could be worn. I found that my daughter was happiest when she was in the baby carrier right up close to me, but that of course will depend on your baby. I would also bring any favorite toy, stuffed animal, or blanket that he has. If you can bring these into the theme park with you, all the better. If he gets fussy, these might help to calm him down. Of course, bring what you usually do for any outing - diapers and wipes and so on. I would also bring an extra change of clothes for him into the theme parks. You can also bring baby food into the theme parks, as well as any snacks that he really enjoys. If he really likes Cheerios, I would take a little baggie of them everywhere - like the favorite toy, it may help to calm him down if he gets upset.
I definitely recommend that when you are in the parks, you take advantage of the
Baby Care Centers. They are located in each theme park, and offer quiet spaces for you to feed, change, and nurse your baby. When my daughter was a baby, I would often feed her in the nursing rooms at the Baby Care Centers. They are quiet, have low lighting, and rocking chairs. It was a very comfortable place to feed my daughter. The Baby Care Centers also offer for sale essential items that you may have forgotten, such as diapers and wipes.
I hope that this information is helpful for you, Veronica. Please do not hesitate to ask if you have any further questions!