I vote to hold off on Disney.
I havent read any of the other post but my husband and I took our annual beach trip to Florida this past Spring. We took our 18 month old daughter. The beaches on the gulf side are AMAZING!!! The water is as close to carribean that you can get around here. It is calm 80% of the time, And the sand....omg, it is like flour.
If you could vacate somewhere around Tampa/Clearwater area you will be highly pleased!! The Lowry Zoo in Tampa (voted one of the best by Parents Mag) is really nice! Busch Gardens is awesome!! They have a Seseame Street area the kids LOVE! They get to meet all the characters. Between the amazing beaches and those 2 attractions, it makes for a really nice, fulfilling vacation.
We rented a condo from a couple who was extremely nice. Their website is www.barefootpassion.com. We found them on www.vrbo.com. Highly recommend these.
Good luck!! Im sure either place you choose, you will make lots of memories! Safe travels!