On the Gulf Coast and near the bottom of the peninsula are Sanibel Island and Captiva Island: two beautiful islands for nature lovers. No beach pollution; visitors find miles and miles of beaches perfect for kids because of the gentle waves and shallow shoreline. The islands are famous for shelling, too. Several family-friendly resorts have activities, watersports, and miles of beach to explore.
Dubbing itself "Orlando's Beach", this affordable west coast area two hours east of Orlando has nature outings, miles of top-rated beaches, and some cultural gems in St. Petersburg. Fun outings include dolphin-spotting, shelling, Pirate Cruise.
This theme park has thrill-ride roller coasters, great water-rides, lovely landscaped grounds, attractive African theming, and opportunities to view elephants, rhinos, giraffes, etc. A fun, pretty park that's manageable to do in one day.
75 miles north of St. Petersburg is one of the best places to see-- and even swim with-- these large gentle creatures in a natural habitat. (November to May are the best months.)
This giant 2400-acre resort has a beach side on the Emerald Coast (Gulf of Mexico) and also a bay side, with many activities: kids' sailing, kids' tennis, kayaking, putting course, Jolee Island Nature Park with pirate-ship playground, and a Kidzone with programs for ages 4-6 and 7-12. Watersports include body-surfing and Boogie boards (complimentary). Kids might also enjoy the Junior Golf Academy, with excellent instructors. Best way to get around this huge giant resort is on bikes. The centre of gravity of this huge resort is the picture-perfect Village of Baytowne Wharf.
In a state park in the "Panhandle" near Tallahassee is one of the largest and deepest freshwater springs in the world. Swim or snorkel in the natural pool above the spring; see alligators on a river boat tour; or do a glassbottom boat ride; dine and/or stay at a historic lodge; take nature hikes.
Our About.com Guide for Florida Travel has 26 suggestions, from Astronaut Encounters to Zip Up Your Saddlebags (- horsey fun in Ocala.) You'll be surprised at the variety.