We did all the "tourist" stuff our first time and it was hotter than an oven and the kids were tired. The aquarium was a waste, Margaritaville wasn't what we expected and the southern most point was anti-climatic. They couldn't wait to get back in the Mickey pool.
Key West is great for the 21 year olds that bar hop.
Next time, I'm going to take the kids to the beach or maybe rent a wave runner or something. Sun sand and water is what it's all about for us! And afterwards we'll get our key lime on a stick!