Hi Rivkah!
Congratulations on your upcoming vacation in Walt Disney World!
I would recommend you take the kids to the Magic Kingdom, Hollywood Studios, and Animal Kingdom. EPCOT is one of my favorite Disney Parks, but for kids it can be a bit overwhelming as it is large, requires lots of walking, and has fewer rides/attractions geared toward children. Mine enjoy it, but they enjoy all the others a bit more at this stage of the game (close in age to your children).
You will be happy to know that most WDW table service restaurants that accept reservations may accommodate kosher needs if ordered at least two (2) days in advance by calling (407) WDW-DINE (939-3463).
There is also a list on the Disney website of Disney quick-service restaurants that offer kosher meals with no advance notice. See this webpage for the list:
Special Dietary Requests at Walt Disney World.
I hope this is helpful in your planning. If we can be of more assistance, come back to ask us more! Have a magical vacation!