Hello, Lisa!
What an exciting trip you're about to take! Your family's first vacation to Walt Disney World!
I highly recommend that you try to keep your pace as relaxed as possible, so that you get to see as much as you can, but a comfortable rate. In order to do so, consider keeping park hopping to a minimum. Think one park each day, heading back to Disney's Wilderness Lodge for a nap / swim in the afternoon. Once refreshed and ready for dinner, you can either return to the same park, a resort restaurant or a restaurant in a different park, if you have the Park Hopper Option.
Let me know if you do have the Park Hopper Option for your Magic Your Way Base Tickets, if you're on a Dining Plan and the dates of your stay. Park hours vary tremendously throughout the year, and there are ways to maximize your dining dollars, depending upon which / if you're on a Dining Plan.
I'd plan on spending more time in Magic Kingdom Park, too, since your little ones are the perfect ages for most of that park; besides, it's where the magic began!
Finally, take a look at this great link for traveling with
Little Ones at Disney Theme Park. It's a great starting point, and may help you generate more questions, too. Feel free to send them my way! I'd love to help you plan the most magical trip for your little prince and princess!