Don't want to get in between what you and riguerin have going on ;-) but I was in Islamorada the begining of the month with my teenage daughter. She just loved it. She is a diver, likes to do things, and is a big time people watcher.
We did a day trip after morning diving and had to be back for next morning diving. So, nothing crazy. But, we walked around (Southern Most House area), caught the sunset , did a little shopping and had a bite. No crawl's, etc. But, we had a nice time and she was pretty entertained by it. We only had time to make a couple of short stops on the way down, so I would think a whole day with some snorkeling would be great.
She loved the Keys, the diving, and Key West and she was just hanging around with her ol' dad.