You do know that Orlando is like 3 plus hours from Miami and Key West is like 2 hours plus driving time. I would just stay in Miami if I were you. There is plenty to do. Go to Bal Harbour.
I was just going to say the same thing... and besides that, if you are goingto Orlando you should really spend some time there and visit not only disney, but universal, islands of adventure, and othr parks... but there's a lot of thing that you can do in miami.
If u want to go shopping u should definitely go to sawgrass mall, it's not in the miami area, but it's totally worth the ride, theres tons of outlets and you'll find great prices. And Bal Harbour has the best stores! LV, Chanel, Dior,
Gucci....
You can go to Bayside, very nice place, and you can take a boat tour to see some celebrities homes. They also have a very nice mall there.
There's the everglades, and the airboat rides, lots of fun...
You have the miami sea acuarium.
There's really tons of things to do in miami, you can have a lot of fun there.
Hope i was helpfull