I used to work there and you dont want to go in August as its very hot and extremely humid. The only reason to go to Orlando is for Disney. Not very honeymooney though. The Florida keys are the best part of florida especially Key West and the reef off Key LArgo. The Everglades are worth a visit also. If you stick to Orlando + Miami most people you'll see will be under 15 or over 55. I would drive down but there is not very much in Miami. I alway found it a bit of a grotty city.
There can be tropical storms in August. If you want to get good weather assured its Nov to May, outside of that anything can happen I'm afraid. If you get a rain shower you just have to pull over to the side of the road and wait for it to pass.