Jennifer,
What an exciting time to go! Great crowd sizes, and the first trip is always the best!
You only have two days that are locked in to the Magic Kingdom, as Chef Mickey's and 'Ohana are both outside the park in resorts. And no, I don't think it is too Magic Kingdom heavy with a 7 and 5 year old. Here is what I would do;
- September 5 - Arrival Day
- September 6 - Magic Kingdom
- September 7 - Magic Kingdom
- September 8 - Hollywood Studios
- September 9 - Epcot
- September 10 - Magic Kingdom
- September 11 - Departure Day
On the 8th, after breakfast, take the resort bus from the Contemporary to Hollywood Studios, as I think your kids would love that park. And as for dinner at Epcot, there are several choices. Since you already have a princess experience, I would recommend either Biergarten (fun atmosphere, decent German buffet), Le Cellier (great food), or Rose and Crown (best of all choices for decent food, great location, and wonderful evening views).
I don't have you visiting the Animal Kingdom, though I do love that park. I think that you can save that for your SECOND trip to Walt Disney World!
Write me back directly with any follow-up questions!
Have a magical (and delicious) vacation!