Hi Erica! Thanks for asking me your question! Disney's
Polynesian Resort has large guest rooms that can comfortably accommodate your family of 5. Rooms at the Polynesian have two queen beds and a day bed, and you can request a crib for your one-year-old, so your family could easily fit in one room. Although the Polynesian is one of the oldest resorts at Disney World, rooms in all of the longhouses were completely refurbished about 5 years ago with new bedding, paint and updates. (Of course, rooms continually receive repairs and refreshing as necessary, and if you ever receive a room at a Disney resort that you feel is not up to par, definitely speak up, as Disney aims to please.) The Tahiti and Rapa Nui longhouses were built several years later than the others, and thus are the "newest" and rooms there are slightly larger.
With your young children, I think you'd love the convenience of staying on the monorail route, and the kids would love the volcano pool. In addition to large rooms, magical views, and a prime location, the Polynesian also has wonderful restaurants, including one of my family's favorites: 'Ohana!
Feel free to visit us again at the Moms Panel if you have more questions! Aloha!