Hi Lisa,
Your children are at a great age for their first trip to Walt Disney World. I love the end of October as a time to visit. The weather is typically very nice, and the crowds tend to be a bit lower.
The structure of your trip will depend a lot on your particular family. Some folks like to save Magic Kingdom Park until the end of the trip, as many children picture the Magic Kingdom in their minds when thinking of Walt Disney World. The idea here is that if your children will be let down by anything that is not Magic Kingdom Park, then save it for last. Another way to handle this might be to separate the Magic Kingdom Park days - doing one earlier in the trip and one later in the trip. This way if your children enjoy Magic Kingdom Park tremendously you can always remind them that you will be going back later in the trip. You may also want to consider what daily crowds will be at each park. The website touringplans.com is very helpful to see what predicted crowd levels are for the days of your visit. You can use this to guide your decisions as to when to visit which park. Typically, the water parks are less crowded early in the week, so you might want to make that your activity for Monday or Tuesday.
If you are staying at a Walt Disney World Resort, also be sure to check which park has Extra Magic Hours during your stay. You may wish to take advantage of this extra time in the parks exclusively for Walt Disney World Resort guests. Although park hours for your trip are not yet available online, you can find the
schedule of park hours for Walt Disney World online. As you get closer to your trip, you can go here to find which park has Extra Magic Hours on each day of your trip.
I hope this information is helpful for you, Lisa. Happy planning, and please do not hesitate to ask if you have any further questions!