My girls will be 16 and 15 at the time of the trip. My niece will turn 8 the second day of our trip and my nephew will be 12 at the time of the trip. My friend that is going with us likes seafood but the rest of us don't can you suggest any place that she can get seafood but the rest of us can eat normal food?

Sorry to be a pain in your backside. Our last trip nothing was really planned except for thanksgiving dinner and that was at tusker house which my youngest daughter wants to go there for her choice. The buffets really help out with the picky eater in our group.
You are definitely not a pain. I remember trying to decide (and I still have trouble even after going 13 times!) where to go with a picky eater.
Okay, so the Coral Reef (Epcot) is delicious and they have salmon, blackened catfish, seafood linguini, mahi mahi for the seafood lover and they also have New York strip and chicken and I believe they had a pork dish. The kids menu definitely has a pizza and I think another offering. We like the atmosphere of the restaurant. One whole side of the restaurant is glass so you get to watch the fish, sharks and rays swim by.
The Sci-Fi (Hollywood Studios) has a shrimp pasta dish, bbq ribs, butcher steak, burgers and sandwiches. Kids menus are pizza, beef and macaroni, burgers and hot dogs. The food has always been good and the atmosphere is fantastic. It looks like you are in a drive in theater complete with old cars (which you get to sit in while you eat).
At LeCellier (Epcot), they serve King salmon, prime rib, chicken, steak and halibut. They had a few choice for the kids including steak, pasta, pizza and hot dogs. The restaurant looks like you are dining in a wine cellar.
We have never eaten at Mama Melrose's but I see that their menu offers calamari, salmon, chicken, flatbreads and butcher steak. Their kids offerings are pizza, grilled chicken strips and spaghetti.
Like I said, some of the counter service kids' choices are pretty limited but we can usually find something for our son at the restaurants I talked about earlier.
Backlot Express at Hollywood Studios has chicken nuggets and sloppy joes for the kids. Adults can order burgers, chicken strups, salads and turkey sandwiches.
Pizzafari at Animal Kingdom has PB&J sandwiches for kids (which I think is dumb in a pizza place) and spaghetti and meatballs. Adults can order pizza, breadsticks, salads and italian sandwiches.
Flame Tree at Animal Kingdom has chicken wings and hot dogs for the kids. Adults can order smoked chicken, ribs, beef and pork sandwiches.
Toy Story Pizza Planet is a great find for picky kids because their menu is the same as the adult menu. It's also a good deal since you can order a combo meal which is pizza and a salad. The place is packed at meal time so it would be nice to have somebody stand by and grab a table while the other waits in line to order. My husband looked for a table and called me on my cell phone when he finally found one.
Let me know if you have more questions.....really, you're not a pain, I don't mind helping out at all!