Hi Megan,
You are choosing between two wonderful resorts!
Disney's Contemporary Resort is sleek and modern, and
Disney's Beach Club Resort is quaint and charming. I am happy to help you think about each of these resorts and how your toddler will like each one.
The benefit to Disney's Contemporary Resort is of course that it is so close to
Magic Kingdom. You are so close that you can take the monorail, a boat, or even walk! Being able to walk quickly to the theme park, or back to the resort hotel for a nap, can be invaluable for a little one. Disney's Contemporary Resort has a great pool and wonderful dining options.
At Disney's Beach Club Resort, you will be able to either take a boat or walk to both
Epcot and
Disney's Hollywood Studios. Epcot is closer and is a shorter walk. One of the best things about this resort is the Stormalong Bay pool area, complete with a lazy river and area to play in the sand. Little ones tend to love this pool! There are also excellent dining options at this resort, and you can easily access many other resorts for dining such as Disney's BoardWalk Inn and the Walt Disney World Swan and Dolphin.
As to which park your little one would like better, I think she would have a fun time at all of the theme parks. Most guests to associate Magic Kingdom, with the iconic Cinderella Castle, the most with Walt Disney World; however, as a toddler my daughter loved running around the World Showcase at Epcot.
No matter which you choose, I wish you a magical vacation, Megan!