We have three boys - ages 14, 13 and 6. We've been taking them to WDW relatively frequently in recent years, and we've been doing character meals at WDW frequently since our youngest son was a year old. Since that time, their unanimous favorite character meal at WDW has been and continues to be Garden Grill.
Everyone loves the characters (Mickey, Pluto, Chip and Dale) and the unique nature of the restaurant with the rotating scenes from the land. We always request a booth on the lower level and that makes the whole experience far more relaxing than any other character meal on property. We love the fact that the food is served family style and comes to the table, so no need to juggle plates or get back to your table for character visits. And the character interaction has been the best we've seen at Disney - at all our boys' ages from the baby years to the teen years! And in our opinion, it's the best quality food of any character meal at WDW - not signature dining by any means, but better than most buffets. Part of the reason I enjoy it so much is that the salad and the bread is really good - always fresh and many of the ingredients are from the Land. The rest is fine, but the salad and bread are highlights (along with the sweet potato fries from the children's selections!)
Over time, we've taken the boys to Chef Mickeys for breakfast and dinner, Ohana breakfast, Tusker House breakfast, Crystal Palace breakfast, Hollywood and Vine breakfast, Akershus dinner, CRT dinner and breakfast, Cape May breakfast - many of these multiple times. We're moving toward more signature dining and non-character meals at this stage, but Garden Grill is the last character meal standing and always on our rotation!