There is no comparison Q and Key West. Everyone needs to do each at least once in their lifetime. I would check with Boyds Campground in Key West and see if you can work out the dates that will suit you. 2 or 3 days/nights will give you the highlights.
We haven't had an RV in Key West, but we stayed at the Fairfield INN there. That was the last week of March 11 years ago and spent $159 per night for a King Room.
If you are retired military, then there will be a dry camping spot for you in Key West, otherwise, unless you have very expensive reservations, you will probably not find any place to camp in the keys. Monroe county, the keys and most of the lower Everglades, does NOT allow dry camping(boondocking) and they strictly enforce their ordinance.