I'm not sure about seafood, but every upscale Disney restaurant we've been to on property, has been delicious. I really enjoyed the upscale restaurant at Animal Kingdom and so did my kids.
We are chain heavy down here . . . just about everyplace you go to near Disney will be toddler friendly. I don't actually eat seafood but my DH does. Seasons 52 is great -- don't know if you have one where you live. Emeril's at City walk is supposed to have amazing seafood. Flying Fish Cafe gets really good reviews.