Ang, unless you plan to visit Miami, remember that Key West is still 2 hours from Miami
If you want to visit KW and can swing it, buy a flight down to there. You'll go from Orlando to Key West in 50 minutes and--believe me--that makes all the difference in the world if your time is limited. When we lived in Port Orange (about 20 miles north of where we are now), it would take us 6-7 hours to drive to Key West. By the time we'd get there, we'd be tired out. Florida's a skinny state, but it's LONG!
For our anniversary one year, I bought plane tickets. We were actually IN KEY WEST sooner than I would have arrived home on my daily commute. I swore I would never do that drive again if it was for a short weekend trip.