When mom came to visit we took a trip to Ballast Point Park to see what it was all about. They had a nice splash area for kids. The only downfall is that it was over crowded and parking is terrible. There is a park there as well, which is very nice. You can also plan an entire day there and bring a lunch or BBQ on the grill. They have a store and a place where you can rent equipment to go fishing on the pier. The pier has a nice view of downtown Tampa. It was a nice day. 
A Pair of Socks 