Hiwaygal and I had similar "looks" (i.e., both our weddings were fairly casual) but we went about it differently. Since my dress was pretty laidback, I wanted someone to do my hair and makeup so I would feel that at least in some respect, I was getting the special treatment. Well, that and I never wear makeup so had no idea how to apply it so it would look good in pictures.
It really is up to you: how comfortable you are doing your own hair/makeup, whether it's in the budget, and whether you want extra jazz on your wedding day (like hiway gal said, it WILL be Florida, and depending on the time of year, it is GUARANTEED to be very hot and humid!).
GL!