Hi Lucy,
It sounds like you are planning a wonderful vacation! I visited the parks when both my sons were babies and had a truly magical time. You're smart to consider the resort location as you plan. I've found that when traveling with infants, location can have a huge impact on a vacation. I've stayed at Disney's Animal Kingdom Lodge as well as several resorts close to Magic Kingdom park and I love them all for different reasons!
When traveling with infants, I highly recommend
Disney's Contemporary Resort. Its proximity to Magic Kingdom park makes it a clear winner in my book. You can walk right to the Magic Kingdom Main Entrance in about 10 minutes and if you plan to have a midday break, taking the Resort Monorail back to the hotel couldn't be easier. Disney's Contemporary Resort is the first stop after you leave Magic Kingdom park on the Resort Monorail, so if your baby needs a break, you'll be back in your room in no time! This is a very stroller-friendly hotel and that goes a long way for me.
While at the resort, my boys loved to splash in the water playground or wiggle their toes on the sandy beach. The dining options are incredible and the rooms are comfortable with plenty of space for your extra baby gear. Many rooms even have a great view of Wishes nighttime spectacular or the Electrical Water Pageant. It's just wonderful!
No matter where you choose to stay, I hope you have a terrific vacation making memories with your family. If you have any other questions, please feel free to ask at any time.
Happy planning!