I did this yesterday for Thanksgiving - I had missed the boat on airline tickets to visit my family - so will be going next week for Thanksgiving instead and wanted to do something special.
Anyhow - I booked the 12:00pm Dine with Shamu online with an AP discount - so the price for me was $27.80. I had a great table with a good view of the pool. The food was buffet - salad, shrimp pasta salad, honeydew melon, rolls with butter, cheesy mashed potatoes, rice pilaf, turkey with gravy, roast pork with apples, squash mixed veg, for dessert strawberry shortcake, carrot cake and red velvet cake. Drinks were included - even wine or beer. There were also kid choices like mac and cheese but I didn't go to the kids section.
The food wasn't the best I've had nor the worst. I was happy and it was nice to have a good meal for Thanksgiving. I enjoyed the whales close up and hearing how the trainers work with them. An added bonus - they take a souvenir photo for you and give it to you included- which is nice.
All in all for the price I paid it was worth it. The amount of food you get for the money is good - lots of choices. Was it worth $30 - only you can answer that for yourself - it was for me - as I had a good Thanksgiving dinner and something fun to do.
If I didn't do Dine with Shamu I would eat a regular meal - say $15 per person and go to the underwater viewing area at Dine with Shamu to see the whales and usually the team members there are more than happy to answer your questions about the whales and tell you stories about them.