Now that two of our three boys are "Disney adults," we are very picky about character meals! We assessed our eating styles and preferences and found that signatures were a much better value for our family. But we still do a few character meals - we just choose carefully.
Over time, we've done character meals at Garden Grill, Tusker House, Ohana, Cape May, Chef Mickey's, Crystal Palace, Liberty Tree (when it was a character meal), Akershus and CRT. Chef Mickey's is no longer in our rotation because it's not a good value for us. On the other hand, at Garden Grill, we think the atmosphere is far more relaxed, the characters are more interactive and focused, and the food is much, much better. We also prefer the family style service at Garden Grill over a buffet at CM. So for a character dinner, we choose Garden Grill. For breakfasts, Tusker House or Ohana.
As others mentioned, a party of 12 will be expensive anywhere. It just depends on what is important to you and how you define a good value. It's easy for us to say that CM is no longer in our rotation, because we've already been there multiple times. And we enjoyed it each time we were there - we just found other character meals that we prefer and discovered lots of great signature restaurants that fit our preferences right now. We know many who love it and return repeatedly. And of course, it's absolutely a Disney classic. Sometimes, those factors make it a good value, especially when you consider that dinner will be expensive for 12 guests!
Good luck with your decision!