Hi Elena,
Your little princess is going to enjoy Disney World so much! Magic Kingdom is the best place to start. Most of the attractions are well suited for young children. Please take a look at Disney's website and check out the
Attractions page. The ones that say Guests "of any height" are the ones for your girls.
Regarding food, your one year old will be able to share meals with you at no additional charge. I do suggest that 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 princesses.
Also, did you know that Disney theme parks have
Baby Care Centers? You can take your daughter to these centers for a nice break from the crowds and all the walking. There are also baby supplies to purchase if you run out of your own. They have disposable diapers, some different brands of baby foods and formula, as well as some over the counter medications.
I hope this information helps, Elena. Have a pixie dusted vacation!