We did a similar trip to Jan a few years ago.
We flew in to Miami, stayed at Bayside for a couple of nights and did a few of the tours on offer there to see the sights of Miami & Miami beach. Then drove dwn to Islamorada, we stayed at the very lovely Hampton Inn and suites for a few days. We did drive down to Key West and spent the day down there. I am glad we didn't stay down on Key West, a day trip was enough for us.
The next part of our trip was at Naples, then we headed to Captiva for a further 4 nights before heading back up to Kissimmee.

Loved all the places we visited on our trip and would return to them all. We have now fallen in love with Anna Maria Island on the Gulf and spend at least 5 nights there each trip to Florida.

Enjoy exploring