H.S.
I've been to Sea World a few times, and while it's been about 11 years, I know it was expensive then, so I can only imagine how much it'll cost now. I just looked up the price of the all day dining, and I say go for it. If I remember correctly, for five of us to eat lunch, it cost almost $60. It looks like the price of the all you can eat package doesn't just include breakfast, lunch and dinner but any snacks that you want in between.
Good luck!