So...the springs aren't "hot." In fact, they're the opposite of it, and one of the best and most refreshing ways to spend a Florida summer. The saying here is that tourists go to the beach, but locals go to the springs.
There are a ton in the Orlando area to choose from. Pick one and head there, you can't go wrong. Now, on busy days they do fill up rather quickly, but don't worry! There's another just down the road. If the one you're going to is at capacity, you'll be able to get to another one really easy.
Also, all the ones I've been at have free air for your floaties (which you will want because the water is cold and deep), so don't worry about lugging an air compressor with you.