Enjoy your trip to the Keys. I disagree with your reasoning (you are still celebrating)--but you go for it.
I will issue my protest of Mango's restaurant. Do not go there for ANY reason.
My brother and his partner had their commitment ceremony last year. They were bumped from the Hemingway house for a heterosexual couple (they did not wish to fight for their valid contract).
At Mango's they were treated so poorly. Food was not served for the first hour of the reception (contrary to the contract), the bartender overmade the drinks causing my mother's bar tab to be reached within the first hour (lots of witnesses including myself who saw the bartender not measuring shots and being generous thus running through bottles like crazy), When the buffet was served it was poorly set up, the potatoes were completely RAW and someone found a chunk of sharp metal in their salad.
Coincidentally, the Restaurant was busy with an off-site wedding and sent all their best staff to work that. It was the heterosexual wedding at the Hemingway House.
What that restauarant did was very wrong and I will urge anyone to not patronize the establishment. You would think in a city such as Key West, this would not have happened, but we very much believe that it happened that way for one reason only.
The drag shows are great. They did the one at Aqua and the show is phenomenal (though exceeds my blushing threshhold b/c of tons of innuendo and expletives throughout. I naively didn't expect THAT much.) Some of the other ones are not as good. Be aware--the drag queens, really include the very hot men in the show. Admittedly all of us ladies were drooling over this one guy--and were quite pleased that the drag queens enjoyed him so much.
Outside of anything else--I only go with my kids, so my trips are geared towards that.
Fogarty's is a restaurant that my mom (a local) recommends.
I don't really have any other suggestions.
I agree that this is not a place you go to for the beach. You go for other reasons. There is one beach you can swim on. The sand is lovely. But you cannot go in teh water without protective footwear.
The bars were fun. Though Garden of Eden....

The top floor allows...you to go nekkid. But it seems the only folks who are nekkid--tend to be the ones who should not be.
Key West is not my favorite place--I'm really not that kind of girl. But those are the highlights from what my (adult) family members took me to b/c they find it enjoyable.
My kids enjoy the fun things like the trolley tour and the pirate museum. I wanted to do Mel Fisher's last time but got veto'd by my sister and her husband who preferred the pirate museum.
I personally do not enjoy the ride down. But then again, it is 7 hours from my house. My mom lives at MM 27. Lots of fun places on that key that she can recommend for a bite to eat or a drink.