Your DDs will talk about SeaWorld long after your trip is over. A lot of people think there's nothing that compares to Disney, but that's completely wrong. Although I love Disney, SeaWorld is absolutely my favorite park. There are so many hidden surprises, and it's supposed to have one of the best kid's areas, too.
I can understand your husbands point of view that you have limited time and Disney stuff takes priority (not sure if that's how he feels). But I have to tell you, when you're first walking up to the entrance and you go past the mini water reefs, your whole mood will change. There something about being near the water and around the animals that's really hard to describe. It will be the least stressfull and most remembered part of your trip. And if your neighbor loved it, and everyone here is saying the same thing, you can't go wrong.
BTW, go into shows at least 10-15 minutes early. A lot of times, there will be pre-show performers, like the SeaWorld mime, and it is hilarious. I have shown tapes of the pre-shows to friends and they howled with laughter. I don't know, SeaWorld is just fun.
And one last thing, I totally disagree about the food being bad. I've taken a lot of trips and hold an annual pass to SeaWorld and a couple of other parks and SeaWorlds food has consistantly been the best. And, it's fairly reasonably priced. The Waterfront Sandwich Grill is a favorite of mine as well as Smokey Creek bar-b-que.
Heck, worst case, tell your husband they serve free beer at the hospitality center. I don't even drink, but it's still a unique experience to go into the hospitality center.
Oh, and don't forget to take DDs to the stables and to see the Clydesdales up close. The Clydesdales pull a (fake cases of Budweiser

) wagon through the park with a dalmation on it, and they stop at a few key places so you can get pics. Ask an employee or check the park map for times.
OH, oh....and get a park map (it has show schedules) when you walk in. DOH! I'm through with my rant.
Good luck,
- John