Hi Jenelle!
This is a great question. The Swan is a nice hotel in a great location. You will be in walking distance to both Epcot and Disney's Hollywood Studios.
When my two boys were that young, they literally loved all of the parks, though they loved the Magic Kingdom the most. My youngest son, when he was 4, loved spending time in the Seas with Nemo and Friends Pavilion in Epcot; he could literally spend the whole day there.
I suggest spending one or two days at the Magic Kingdom, one day at Disney's Hollywood Studios, and one day at Epcot. If your children love animals, then you might want to visit Disney's Animal Kingdom as well. All of the theme parks have rides and shows suitable for guests of all ages. I know that may sound strange if your only experience is with regional amusement parks, but it is true. Most of Walt Disney World was designed with the whole family in mind!
Since it is your first time, I highly recommend picking up the tour book "The Complete Walt Disney World" by Julie and Mike Neal. It is a great book for first time visitors as it is full of information but is not overwhelming. It is also a beautiful book full of color photographs. It will give you a good feel of everything there is to do at Walt Disney World.
With regards to other reservations, you might think about making a reservation at the
Bibbidi Bobbidi Boutique. It is relatively expensive, but every parent I have talked to who paid for the experience for a young girl has said it is worth every penny!
I hope this helps! Please write back with more questions!