Hi Alison! January is great time to visit Walt Disney World: the crowds and the resort rates are often at their lowest then. The Florida weather in January is hard to predict: it can be really warm or downright chilly. If it's too cold to swim, you'd want a resort with other fun things for the little ones to do, and I think the
Animal Kingdom Lodge would fit the bill! My kids love standing on our balcony overlooking the African savanna and trying to spot giraffes, zebras, and other exotic animals. Another benefit of this resort if it's cool during your trip is that the lobby is connected to the guest room hallways so you don't have to walk outside to get to your room, unlike resorts with separate buildings such as the Port Orleans, Grand Floridian, and Polynesian. If it is warm, the Animal Kingdom Lodge also has a large pool with a zero-entry area perfect for your three-year-old as well as a fun slide your five-year old will love.
You might also want to consider the
Contemporary Resort. Staying on the monorail route is so convenient when you have young children -- it's a snap to go to and from the Magic Kingdom. If you're staying at the Contemporary, you won't even have to go outside to catch the monorail, a real benefit if it's a little chilly. Plus the Contemporary is home to Chef Mickey's, a great character buffet that your kids would love, as well as lots of fun shops.
Thanks for visiting us here at the panel, and feel free to ask us more questions!