Miami and Nearby Fort Lauderdale: There are lots of cruises that leave through the Miami Cruise Port and Port Everglades, so you can also combine a Miami vacation with a cruise.
Amelia Island (Near Jacksonville): Amelia Island offers lots for families, including 13 miles of beaches, golf courses, delicious restaurants, and fantastic resorts
Marco Island: located about an hour from the Southwest Florida International Airport (Fort Myers), offers a beautiful beach, fabulous food, and fun water activities.