My 9 year old DD also loves seafood and she was majorly disappointed with the Mahi-Mahi on the kids menu at Coral Reef. It was a tiny, tiny portion, and as I recall, the only seafood option for kids.
We are going to try Fulton's this summer - they have a few more kids options for seafood, although they are a little pricier. I have never been to Cape May for dinner (not a big fan of buffets) but I agree with the previous posters that it would be better than Coral Reef as far as variety is concerned.