I'll give the DC one a shot for you, but as I've never been to Aquatica (yet!) I can't comment on things to do there.
But, DC...
Firstly, you can eat! There's a lovely breakfast on arrival, then throughout the day the menu changes to lunch, and there's plenty to offer! And as it's all-inclusive you can head back as many times as you like. There are also drinks carts dotted about too, which offer soft drinks and certain alcohol. These are also inclusive, so you can grab one from an attendant whenever you're thirsty!
Then, there's the overall beauty of the place, it's a wonderful place of discovery (hence the name, I imagine!). You'll be able to go to the bird aviery, where you'll find many different birds and deer which you can feed with the food provided by the DC keepers. They'll happily chat about the various birds too, they're lovely.
You can also view the dolphin swims from the side too, which are great fun to watch. Even if you're not going to swim with them, you can still sit and watch. It's fun to watch everyone interact with the dolphins, they're adorable. You can also view the area where you can swim with the rays, many of which you can still view from the side. Infact, if you're not overly scared of water, up to about knee height, then you'll be able to go in this pool, as it never goes much deeper than that. You'll get to touch and feed the rays in here and it's always supervised by staff, so if you do get into any distress, they'll help you out of the pool.
The only place I wouldn't recommend would be the reef, where you can snorkel with the rays and fish. If you're not a confident swimmer, then I would recommend to miss this entirely! It's very deep and cold, so probably wouldn't suit you from what you mentioned.
I'm sure you'd still have a great day here though, there's plenty sun loungers too if you get there early enough. The place is lovely, so sitting by and people watching may also be fun for a while.
Hope that helps...
Hope you get some answers on Aquatica!
