Hello Alice,
Welcome to the Disney Parks Moms Panel! A
Walt Disney World Resort vacation involves quite a bit of walking; there's so much to see and do that it can be very exhausting if you "over-do" it trying to fit everything in. One thing that I always advise when it comes to visiting the Theme Parks is to sit down with your family, pick a few "must-do'" Attractions, and then let the rest of the magic just fall into place.
You have made a great choice in purchasing
Park Hopper Option Tickets. During my family's many visits, we have loved having the flexibility that a Park Hopper Ticket provides. You can start your day at one Theme Park, head back to your Resort for a nap or pool time (which I highly recommend), and then end the day at any other Theme Park that you wish to.
Based on my experience, you should plan for about six to eight hours for each Theme Park per day. This time frame includes breaks for meals and stopping for rests. It's important to take things at the pace of your children so that you aren't too tired to enjoy all of the magic. I also advise planning for two separate days in Magic Kingdom Park. As far as how many miles you will walk each day, I would prepare to walk somewhere between six to ten miles depending on how much time you plan to spend in each Theme Park.
Another thing I suggest is renting a stroller. I used a stroller with my youngest daughter up until she was seven years old; having one was a huge help toward the end of our day when she was tired. You may find that with four kids in tow you'll need one just to store and carry backpacks and shopping bags in addition to a place for tired little one to rest.
Please visit us again if you have any additional vacation planning questions!
Magical Wishes,
Susan