Like others have said, it does depend on your children....
Last Sep we did:
Crystal Palace: we went for Breakfast as you can get into MK before it officially opens....the food was great and the opertunity to take photos without anyone else in front of the castle was fab....but this wasn't our best character interaction.
1900 Park Fair: We went for dinner with cinderella, step sisters and step mother, prince charming....We loved the food and location.....the best thing was the character interaction...My DD4 wore an anistasia dress I had made, the attention she got was the best ever....The step mother saw DD first and took her by the hand to go and meet anistasia...on seeing my DD anistasia shreeked with joy and sat on the floor talking to her for at least 5 mins...she later came to our table and wrote a personal message to my DD and kissed her autograph book, she stayed at our table for at least 5 mins.....then as anistasia went to other tables, she asked them if they had seen the mini anistasia.....if they said they hadn't she would shout over to my DD and tell her to stand on her chair........My DD had the best evening ever!!!!!
Garden Grill: We went here for my DS10 who loves chip and dale....the meal wasn't great but loved the rotating resturant and as we were sat in a booth, you couldn't see anyone else in the resturant....it felt like we had the characters to ourselves....I had made DD a chip and dale dress and DS a chip and dale tshirt for this meal.....chip and dale made soooo much fuss over them both and took them both by the hand and walked off with them....the Character handler also asked if chip and dale could have a photo of DD's dress.....characters were fab, but I don't think we would go back as the food was poor.
Hollywood and Vine: Little einstines and Jojo's circus...breakfast, food wasn't great and character interaction wasn't all that good....we wouldn't go back here.
sorry for going on a bit, but hope the info might be of some help......
we are going back to Disney in 2011, we will definatly do CP for breakfast and 1900 for dinner......we are also going to try Chef Mickeys and Akershaus