Hi Marcela!
The kids are going to love Walt Disney World! The parks are well suited for young children, but I'd definitely start at Magic Kingdom. Take a look at the
Attractions page on Disney's website. The ones that say Guests "of any height" are the ones for your kids.
I also suggest you look at
Disney's Planning for Pre-School Kids & Little Ones page. It will help you plan a kid friendly vacation for you and your family. Another thing, the parks do have
Baby Care Centers. You can take a nice break from the crowds, and have quiet feeding and changing times. There are baby supplies there that are available for purchase if you find yourself in need of something for the baby. They carry disposable diapers, a few different brands of baby foods and formulas as well as some over the counter medications.
I hope this information helps. Have a pixie dusted trip, Marcela! Thanks for visiting the Moms Panel.