Hi Christen!
The Flying Fish Cafe is one of the best, if not the best, seafood restaurant on Walt Disney World. I really enjoy eating there. However, it can be a little noisy so if you are looking for a more romantic atmosphere, you might consider
Narcoossee's in the Grand Floridian Resort.
The Boardwalk area is a nice area and has some "carnival type" games and usually some live entertainment in the evenings. You can also walk around Crescent Lake, or rent a bike or a boat from the Yacht and Beach Clubs. There are definitely things to do with a 10 year old, but maybe only an hour's worth (unless you walk around or rent a boat). If you do walk around Crescent Lake, be sure to stop by Beaches and Cream, the ice cream parlor in the Beach Club Resort. It's fabulous! It's definitely worth getting a table and eating inside if the wait isn't too long!
By the way, since you said it's your first visit, I highly recommend picking up the book "The Complete Walt Disney World" by Julie and Mike Neal. It's a great book for first time visitors because it has just the right amount of information without being overwhelming. Also, it's a beautiful book full of color photographs. It will give you a good idea of everything there is to do in Walt Disney World.
Enjoy planning and write back if you have any more questions!