We’ve done the keys twice, and really like the middle keys best, Marathon, and Islamorado. We stayed at Curry Hamock State park, and really liked it, but you will have to luck into a cancellation.
Since y’all like to Paddle, the different springs in central Florida are amazing. The Rainbow River, Manatee Springs, Crystal River are all worth seeing.
Our last trip to the springs with 12 and 14 year old, we did 3 days at Disney, and 3 days paddling, and both kids said they wished we,d spent the whole week paddling and skipped Disney.