THere are LOADS of waterskiing places in Orlando and on the coase - our favourite is LAke Buena Vista Watersports - have known Dave and Angie for at least 15 years - they taught me to ski, and you can rent a boat out for an hour with driver, take tubes, jetskis, sit by the beach -it is really great -for get snow in summer for heavens sakes -get to Blizzard Beach if necessary!
Sounds like the kids were bored with just beach, so I reckon some time in ORlando may sway it, with Captiva afterwards - or why not fly into,say Texas, and drive down through New Orleans - the worlds your lobster as Peter Kay would say.