Are you speaking of renting one to commute around Orlando, or are you thinking of driving it from wherever you live, to Florida? If the latter, you may have a hard time with that.
First off, have you driven a van this size? If you haven't, I suggest you rent one at home one weekend to experience it. The handling is difficult if you are not used to it, but that isn't the only consideration. Normal 15-passenger vans have THE roughest ride you can imagine, and the seats are vinyl benches that are hard to say the least, and get absolutely broiling hot in summer. A long-distance trip in one of these is my idea of the 7th circle of hell.
In addition, many rental agencies are trying to limit their liability and protect their inventory by refusing to allow vans this size to be taken out of state. (See the previously cited article about why they are worried about losing the vehicle.) If you do manage to rent one for a long-distance trip, in most cases, your regular vehicle insurance will not cover a rental van of this size, which means having to pay the daily fee for the additional insurance coverages. Also, FWIW, the gas mileage tends to be abysmal, you'll spend a fortune on fuel with it fully-loaded.