We're getting married in Key West too - June 2010. I've been about four times and love it more each time!
Restaurant ideas:
Seven Fish is fantastic for seafood (and anything else).
305 296 2777
Good Life
I went there in May 2009 and they had only been open less then a year. The food was tremendous and the service was excellent. Their website is not working, so I don't know if they survived the bad economy.
(305) 296-8484
Blue Heaven
This place is a hoot (in a good way) - outdoor dining with roosters wandering around. They are known for their Sunday brunch (which is excellent and there is always a wait), but dinner is very good too.
(305) 296-8666
Help Yourself
Great breakfast & lunch spot for grab and go sandwiches, salads & smoothies. All organic. Only a few benches outside for sitting, but you can take it and have a picnic on the beach.
305.296.7766
915
When I ate here, my friend and I just ordered a bunch of appetizers to split for dinner - everything was excellent!
I second El Meson de Pepe
Good food, great mojitos and your can easily hit Mallory Square before or after dinner for the sunset celebration.
Another great sunset spot: last time I was there (May 2009), my friend and I had drinks at the Pier House Wine Gallery Piano Bar. The bartender sent us out to the private deck for the condos next door (which were relatively empty) and we had a great, private view of the sunset while we sipped our drinks.
Have a great time in Key West and a wonderful wedding!!!