Shannon:
With preschoolers, proximity to the theme parks makes naptime simpler. Because you'll probably spend at least one or two days at the Magic Kingdom, I'd look at
The Contemporary. Not only will it be only one monorail stop away from MK, once you're in the hotel, you can hop on the elevator and get to your room much quicker--and out of the elements--than compared to the other monorail resorts of the Polynesian or Grand Floridian.
But proximity equals price. If you have your own car and find that you want to spend less of your budget on a hotel and more on character meals, consider
Art of Animation or
All-Star Movies. Both offer Disney character theming and budget-friendly rooms. If these two value resorts swing the pendulum too far, look at the mid-priced
Swan resort with boat access to Hollywood Studios where the kids will see all of their Pixar pal friends as well as Beauty and the Beast, the Little Mermaid and the Muppets. While you won't be able to purchase a Disney dining plan and MagicBands will not come with your reservation, it is a good compromise for value and park proximity if you're looking to visit more than the Magic Kingdom.
Wishing y'all a magical vacation!
Whitney