Stop at Knaus Berry Farm on the way to/from FLL for cinnamon rolls and strawberry milkshakes. The boat tours out of the Flamingo Visitor Center are worth it and kid friendly if you have time to/from FLL: https://www.nps.gov/ever/planyourvisit/flamdirections.htm Feeding the tarpon at Robbie's in Islamorada is super touristy but I bet the littles will love it. The restaurants at Hawks Cay Resort are good. Some are pricy so look at the menu before making a decision. I will think some more. I have a lot of recs if you go to Key West at all.