I second what schoech1 said.
I have camped over 25 times in the Keys and my fav spot is like I said and he did right in the middle. Marathon - Big Pine Key area.
You can also look for trailer(mobile homes) for rent there as well.
Capt Tony's is OK but you need to make sure you get to the 'No Name Pub' in Big Pine.
Xcellent pizza and great scenery inside.
The whole inside of the restautrant has dollar bills stapled to the walls.
It is tradition for folks who visit to write something/ANYTHING on the bill and staple it to the wall.
Some of the things you read are insane.
Take a look....
No Name Pub, Big Pine Key, Florida, Florida's Famous Pub Pizza
I sometimes make the ride there just for a luchtime pizza and come home as round trip is about 300 miles or so for me.
As you get closer to WPB let me know thru PM maybe if space permits y'all can stay here for a night and head down in the morn as driving over the overseas Hgwy at night is very dangerous.
There are many miles with no streetlights and they are old two lane roads in the middle of NOWHERE. Best travelled when the sun is up
The last 200 miles or so can take the longest cuz as mentioned there is ONE road in and ONE road out. It is the same one, US1 otherwise known in the keys as the overseas Hgwy.
A simple fender bender can back up 100 miles of traffic and take six hours to clear.
Once you get into the Middle to Lower Keys please drive slowly as we have a very rare species of deer here. They are endangered and called Key Deer. The biggest "buck' If you can call it that you may see is all of about 40lbs.
They are tame toward people because even though it is illegal to do so folks hand feed them.
The deer have learned to come out and stand close to the roads because they know that vacationers will say 'OMG stop the car lemme take a pic'.
When you get out they come up to you for food.
I admit it is a popular thing to get an order of Fries to go from No Name and then go feed the Key Deer. One of the roads most famous for this is about 10min from the pub.
Go down the road, stop, turn off engine and get out with the Fries...
They will smell them and come out of the woods for a look.
If your patient and move slowly they will come right up and nibble a fry from your hand.
The gilrs should really like that....gimme time I have pics somewhere of 'someone' doing that. I'll see if I can find them and scan one for one.