Wow - 2 weeks - how wonderful for your first trip.
3 Character meals in 2 weeks is definitely not too many if that's what you're asking. And you have picked some good ones - Garden Grill and Chef Mickey's are both great. I have wonderful memories of my daughter dancing with Mickey at the Garden Grill on her first trip - she was 4. We went to Chef Mickey's last time - be sure to do the Napkin Dance! 1900 Park Fair seems to have changed since we were there last, but the buffet was decent.
We are doing 3 character meals in 6 days - Liberty Tree (a new one for us that is often recommended), the new Princess bkfst in Norway, and Cindy's Bkfst - I have two DD's who love princesses.
Spacing them out will be great - starting and ending your trip with them sounds great. I love the idea of ending with Chef Mickey's - you will love it!
You don't say how old your DS's are or who they like - if they like Pooh, I've heard great things about the Crystal Palace in MK, but never have made it there. Also have heard good things about the Donald's Breakfastosaurus in AK, but can't quite squeeze it in this trip!
Have a wonderful time - sounds like you're off to a great start!
I will be taking my 2 DSes to DW for 2 weeks in july(this will be our first time!) I have made PS seatings at three different places. our first full day at 1900 park fare for Breakfast-one week later Garden Grill for lunch_one week later (our last day)CHef MIckeys for breakfast. do you think this will work or does anyone out there have any better suggestions all would be much appreciated!!! mimimom 
