We took our kids to Goatfeathers a few months ago and had a poor experience. BUT, we decided to try it again, just to give it a fair shake. Unfortunately, our second time around was no better. The service was adequate, but the food was extremely disappointing. Not only was it very late to the table, but the seafood really tasted like it had been frozen (we were expecting fresh seafood). And the prices were just as high as anywhere else on 30A.
We also went to Elmo's a few months ago. While we thought the food was "okay," it was overpriced (in our opinion).
We have 4 kids (the youngest being 8), and we've just about reached the conclusion that, rather than trying to take everyone to what appear to be "family-friendly" places (The Crab Trap, Goatfeathers, Elmo's, etc.), we're just going to start taking them to the places that we love (D&K, Cafe 30A, 331, etc.). Generally speaking, the prices are no different, but the quality of service and food is significantly higher.
Obviously, these are just personal opinions! Someone else may have better advice...