I don't know. The DISboards website says that Storytellers has characters at their meal, but someone in this post says they don't. The website doesn't say whether or not GK has characters.
Goofy's Kitchen has characters everyday including holidays. We have eaten there for Easter; the characters were there. The food was the usual fare for Easter. I have read that for Thanksgiving and Christmas, seasonal items are added to the menu.
Storyteller's normally only has characters for breakfast. Lunch and dinner are non-character meals. Of course, for special occasions, Disney could decide to add characters, and I guess this would add to the experience of a holiday meal such as Thanksgiving. I can only tell you from personal experience of eating Thanksgiving dinner at Storyteller's for each of the last four years that there were no characters present during dinner. We ate between the hours of 4 and 7 PM each year. Our family enjoys character meals, but I actually like Thanksgiving at Storyteller's in part because it's not a character meal and, therefore, seems more peaceful and relaxing to me. I have heard that the Thanksgiving dinner at PCH Grill in Paradise Pier is somewhat similar to the Storyteller's meal (again, no characters), but I have never tried it.
If the pattern of the last several years holds, then you will need to go to Goofy's, Ariel's, or the special meal at the DLH ballroom to have Thanksgiving dinner with characters. Of course, Disney could always change something or add something new this year, but we won't know about it until much closer to the date.
I also don't think we are doing a traditional Thanksgiving dinner. This is a cheap trip for our family. lol
My family and I will be at 
