Hi Rose,
I have really tried to find a way to explain why Epcot should go first before Magic Kingdom. The best way I can describe it is to imagine a rose. A closed rose and an open rose are just as beautiful. However, everyone likes the open rose because it is vibrant and full of life which is Magic Kingdom. Yet Epcot, is like a closed rose, just waiting to open and have you enjoy the beauty.
The fun in Epcot is subtle. It's buildings are clean lines and hard surfaces. You need to go inside to see the fun. For example, the Land can show you how to grow a Mickey Mouse pumpkin or have you hang gliding over California. You can journey into space or design and then "race" your car around the a test track.
Once you finish touring what the future may bring, you can travel to 11 different countries and explore their cultures. You can eat in Morrocco or visit the Eiffel Tower. It is a great way to introduce children to other countries. They can be an international tourist and collect stamps of all of the countries. They can also help
Agent P save the world.
The other reason is because it is a big park. It really is two parks in one with a lot of walking. Going to this park on fresh legs and being well rested also helps.
If you can change it without it impacting your other items on your itinerary, you might consider it. Also, remember it is your vacation and ask your children what they think. If they naturally love science and exploring new things, then you may be fine.
Wishing you a magical vacation!
Beth