Which 佛羅裏達 beaches to visit at Christmas?

 

This will be our first trip to FL. We have booked 7 days of trip in Disney at Orlando this Christmas. After that, I am thinking to enjoy some beaches for another 2 to 3 days.

There are too many beaches in the west from Tampa to Fort Myers/Cape Coral, and also in the east coast from Cocoa to Miami... Maybe not Key west this time since it's another 3 to 4 hours of driving...

Could you please help to recommend which beaches we should visit for 2 to 3 days? Should we do it along the west or east coast? I guess it's too cold to swim at Christmas time, but really want my kids (1, 4 and 7 years old) have fun.

Thanks!