We are in the Keys every year for Christmas.
I bring a four foot live Christmas Tree and we put it on the picnic table.
There are very few mosquitoes, but as soon as it gets dusk, the no-see-ums come out.
Get a "thermocell" and you can sit at your picnic table all night and they won't bother you.
If you hit the area at the right time you can see one or more of the many decorated boat parades.
The Keys are very festive at Christmas and you will get a kick out of seeing all the displays showing a "white" Christmas
Jack L