@CyndiLouWho said what I was going to say. I've driven the uhaul across the country from WA to NC and back and I don't care if I move 10 miles across town I'm not doing it myself. Though with that short I'd be fine driving the truck but not the loading and unloading. Anything out of state someone else can do, ESPECIALLY if someone else is paying for it.
It's a giant pain in the butt and it's not fun. If you did it yourself you'd have to tow one of the cars, because really either way in order for the cars to be there when you get there they'll have to leave IA before you do. Or they leave when you do and you are car less in FL and have to rent. Either way I'd drive one of the cars down and let them move the other. Cost wise, it's not going to save anything and someone else is paying. It's just more stress. They aren't fun to drive, you have to rely on your mirrors and be a more confident driver than you are in your car.
And then there's the whole, Someone else is PAYING to move the stuff so you don't have to. Pack up the car with the guitars, some clothes, the cats, valuables and any papers that are sensitive that you don't want lost. When you sit and think about it, the car is for the stuff you don't want to lose but it's stuff you wouldn't want/be able to take if you did fly, not even thinking about the cats. But the bed that the movers move or the box of towels etc, I can live without those for a few days and I have insurance so if something happens to them I can just go buy new ones. But moving sucks, take the stress out of doing it yourself because you can.