Whenever we drive down to FL., it seems like half the cars on the interstate have multiple bicycle racks on them. Yes, I'm just one state away, but I notice license plates from all across the country carrying family bicycles on their FL trips.
Although I used to own an expensive touring Trek for long-distance rides in hilly terrain, I agree with Red that $300 bikes would prove more than adequate for Florida terrain and casual riding.
That said, there is another consideration. The gear shifts on the new bicycles are nicer than the older ones. You don't have to judge how far to move the stick for a certain gear. So if you're looking for an excuse to get new bicycles, I offering that one.