Downtown Tampa has so much to do that if you haven't checked it out recently, you should. Look over its website and you will find something for people of every age. The Riverwalk is great, there are lots of restaurants, museums, parks, and a theater.
Another great thing about Downtown is that you will have access, via the street cars, to Channelside and Ybor City. Downtown is fairly bike friendly, if you stick to the Riverwalk and the trail to Ybor.