Discovery Cove, your food is included, but not dinner. More lunch type meals in the middle of the day with snacks and beverages included all day. Since the park closes early, like 6 or 7pm, dinner off site is usually a must.
Sea World also closes really early in September, so you more than likely wind up off site for dinner.
Orlando Ale House. There's two of them, one on John Young Parkway and north of Town Center Blvd, in Hunter's Creek. The other is a block north of DTD entrance on 535. Both of them can be fairly crowded.
Logan's Roadhouse. This is located in the Publix shopping plaza on International Dr S and 192, Just south of Gaylord Palms. I love this place and they usually have 2 meals for 15$, 1 entrée and 2 sides with each meal. The sale is Mon-Wen all day or weekdays 4-6pm.
Tavern on the Lake. Located north of Disney property, near the Metro West area. They have certificates on the restaurant.com site. The food was good, but keep an eye on the tab even with the coupon.
Smokey Bones. Never tried it, but I've heard it's really good. Located on 535 and 192 in the Publix shopping plaza.
Sonny's. I love a good BBQ, and they have great sweet tea. Reasonably priced and sometimes a little cheaper than the average sit down. You'll have to google this one, I know there's one out in St Cloud, but probably not the direction you want to go.
There's usually buy 1 get 1 free coupons for Medieval Times on 192. Never been there myself, but never heard of a disappointed customer either.
If you want expensive, you could also try the restaurants located inside of Gaylord Palms, if you've never been there. If you do eat there, they will validate your parking. I've eaten on the boat one, and loved it. Never had the money to try the steakhouse one.
Crisper's is a salad-soup kind of place, owned by Publix. There's one located in Hunter's Creek in the Publix Plaza.
As far as right next to Sea World gate, which would only take you 20-30 minutes extra for eating off-site rather than on-site.
There's a Friday's, KFC, Wendy's, McD's and a few others.