Wind: The Keys will give you more consistent and reliable wind. For kiting, December is usually a good month for Florida, in general.
Lunch: I can't comment on "lunch spots" (if I'm kiting, I skip lunch).
Crowds: There are fewer launch spots in the Keys than in the Tampa Bay area (if you include Ft. DeSoto and Clearwater area beaches); but if you have access to a boat in the Keys, you'll be fine. Tampa Bay area is crowded on the highways and roads, but not bad on the beaches.
Things to do when no wind: Depends on what you like to do. If you want to shop, go to sports events, go to bars and restaurants, then Tampa Bay is better. If you want to scuba dive, snorkel, SUP, and also go to bars and restaurants, then the Keys are better.