I'm just back from 2 weeks in Florida. Went with friends so had 5 kids (10, 9, 9, 8 and 5 yrs)
I would say go for a villa, it is unbelievably cheap (ours was £700 for 2 weeks had 5 bedrooms, own pool, big garage, fully equipped) and is nice to have your own space at the end of a usually busy day.
We went first 2 weeks in July, it was crazily hot and quite rainy. Have heard easter is very busy.
I would say in 2 weeks we still had lots we could do, so no less than that.
We had 14 days unlimited to all disney parks and universal parks. I think Disney is a must as as well as the usual stuff there are water parks and the animal kingdom is good if animals are of interest...Universal was also a big hit (new harry potter world if your boys like that?)
If your boys like lego there is a big lego place in downtown disney, with computer games and building areas and stuff.
I have to say that i thought all the water tasted like detol, so i could not drink from any of the water fountains, but buying free refil cups were a good buy
Malls are good, lots of bargains to be had
Agree with getting a guide book and try to plan things the night before
A car is a must, we got a 15 seater van/bus/car thing cost £690 for 2 weeks and we used it every single day and the full tank of petrol never ran out.