Go with your gut! $1000 is alot of money!
DD (10) and I just did this our last trip. I had received an unexpected bonus and thought I might never be able to justify that amount for a single day again. In hindsight, we did have a really nice day; but if I had to choose between spending $500 for 2 of us to do DC again and an extra trip to Fla in the winter with $100 RT airfares and 3 nights at an inexpensive hotel, I'd go for the latter.
A few thoughts from our trip...
We did the dolphin swim first thing so we had the rest of the day at the park
When I called DH at around noon time, I told him him DD enjoyed the dolphin swim, but was scared of the stingrays in the pool, Was scared of the stingrays in the coral reef, and was scared that a bird would land on her in the aviary. I was REALLY regretting the purchase right about then.
Later, she did warm up to the stingrays and actually really enjoyed going in that pool. She became very proficient with the snorkel in the lazy river, but still wasn't too thrilled about the the coral reef because of the really large stingrays there. And she loved swimming around the lazy river. We stayed until closing and since we're taking a cruise next November I've chalked it up to a great "trial run" for opportunities we'll get for our shore excursions. Plus, maybe she'll do the snorkel at TL.
IF the $$ are a big concern, maybe consider just letting the kids to the Dolphin Swim