I would consider St. Augustine; it's got history, typical beach town attractions, Ripley's Believe It or Not!, a pirate museum, and Anastasia State Park is nice and is right on the beach.
St. Augustine is pretty awesome. You and your wife will probably love it. The historic district, Alligator Farm, Ripleys, http://www.nps.gov/casa/index.htm
. The kids would probably love the Cape more but St Augustine Beach is better.
DO NOT stay at Vilano Beach. Stay at St. Augustine Beach. Vilano is made up of crushed sea shells and is awful.