If you want to do the dolphin experience it is possible to do this in water that is waist deep, obviously it isn't quite as much fun as getting a free ride from one , but it's still pretty good. If you don't do the dolphin swim then the price ( $100) for a day in DC, lunch and a week at SW is really pretty good, if you use the SW passes a couple of times).
At DC , you'll get a lot of pleasure from watching your children swim with the dolphins, my daughter couldn't stop smiling ALL DAY. There is a nice aviary, where you can feed the birds ( and deer) , the stingray lagoon is only waist deep so you can just stand up and let the swim between you. There is a pool that you can cool off in and splosh about it. With the boyancy of seawater and your lifejacket, you may find you feel ok to try the coral reef snorkle, you will float on the surface so as long as you can manage the snorkle to breath you should be OK on this. It is a really relaxing place to spend the day, I don't think you'll regret going.
