I'm so happy that you asked about leaving pets outside alone. Florida is a dangerous place for cats who wander off. My 3.5 maltese was outside with me when I saw a huge (estimate he was over 1.5 feet tall)
hawk swoop down in the next yard. I believe he saw the one and only rabbit ever seen in these parts. I didn't wait to see if he was successful. We also have huge owls who hunt at night. Since your cats are fairly old I wouldn't chance the fact that they could find their way home. A friend recently told me that she saw a coyote in her older and densely populated neighborhood and I know that they are frequently seen in the newer areas being built. I haven't mentioned the gators that are all over the place should you live near water. It can be a hostile environment for domestic animals so keep them close. And then there's Fumar......