I'm in MD and can't help with any easy collecting spots in FL - sorry.  I'm sure someone else can though?  I'm sure you've already done this, but for the heck of it I googled "Florida Fossil Collecting" and clicked on the link: http://www.flmnh.ufl.edu/vertpaleo/vppermit.htm.  It was interesting to read that for land owned or leased by the state of FL, you need a Permit in order to perform "systematic" collection "most" fossils, but NOT shark's teeth, invertebrates, etc.  - read the paragragh on "What's Covered" for details.  This apparently applies to both residents and non-residents.  It sounds like as long as you're not there for more than 3 days in a row, or using heavy machinery, etc, you don't need a permit and you can collect anything you want!!!  I had to laugh at paragraph 3 under "Systematic Collection" which also has a time stipulation :  "...or a maximum of twenty-four hours during a period of one year".  I had to laugh at the 24 hr limit, which to me implies the total/cumulative number of hours.  I would surpass that in one or two weeks and have to take  the rest of the year off - ya right!

Hope you find a place to take the family.  If the kids are real young, your best bet might be a nice open beach where the dangers (except for water, sharks, jellyfish ) are a minimum.

Daryl.