Lots to do in Key West....
You can walk Duval St... pick up some livations at one of the establishments and start walking. Lots of shopping and can always stop for a refill at another hot spot. There are some really neat bars along the street including Hogs Breath, Sloppy Joes... the Garden of Eden( a real eye opener!!) and many chains .. Hard Rock, Fat Tuesdays... and Margaritaville.....etc.
Once you get to the eastside of the street... head down to the southern most point for your required photo op!!
Mallory Square (where the ship docks) will have lots to offer...shopping.. sight seeing tours and such. If you don't want to do a ships excursion... which I wouldn't recommend... checkout the internet for Key West... there is alot to do and see in Old Town. www.keywest.com
will have links to many of the things to do on the island. 8) 8)
In my trips to KW i have never done the Hemingway House... so cannot speak for it. Might be interesting if you are into the history stuff.