I lived in Clearwater for a time and would spend hours on the beaches there. The water tends to be warmer on the Gulf side and the sand is also different from the Atlantic. If you want more of a crowded beach experience with restauraunts within walking distance and several hotels, go to Clearwater Beach. You will have lots of parking, but it is metered ( I think it still is anyway) There are lifeguards and I think still volleyball courts.
If quiet and pristine is more your thing, check out Caladesi Island which is in nearby Dunedin. You have to take a ferry boat over there and it is a state park so there is a charge to enter the park (small and paid by car not people) and there is a fee to go over on the ferry but it is well worth it in my opinion.
There is a really great beach I go to near Cocoa that is called Cherie Down park. It is also a county park but the parking is free and you simply walk over a bridge onto the sand. It is at Cape Canaveral (right down the road from the Port where you will pass the cruise lines. There are lifeguards there as well.
.
Jetty Park is right down the road, but there is a fee to get in. But many people like going there. Lori B Wilson park is also a nice beach area, but it is farther down the road than the first two I mentioned.
As for water parks, we have been to both parks this summer more frequently than the beaches. We like the wave pool and the slides and lazy river.
I hope the information is helpful.
My personal choice would be to do the water parks in October. One of the two will be open while the other undergoes upkeep.
Even Clearwater beach water is not going to be as warm as they keep the water at the water parks.
Have fun with whatever you decide.
