Luv4Disney said:
I saw people with these very light weight backpacks on. It actually has water in it with something to keep it cooler. Then it has this tube and mouthpiece thingy that goes right to your mouth. It sounds complicated, but it wasn't at all. It was so neat we asked where they got them. You can get them in Sports Authorities and places like that. We'll be getting them for our next trip (plus, saves money on buying water since the water fountain water is kind of gross). Also, those frozen neck things from Sharper Image? Yeah, they don't work, especially in Florida.
The backpack things are commonly called hydration systems. I have two (different sizes) and use them regularly. You can buy them at sporting goods stores as well as Target/
Walmart in the sporting goods sections. I have a Nalgene system that I really like. It's a little bit larger backpack (so I can take other stuff with me) that has a three liter, insulated bladder (that's the thing you keep the water in) and a shut off valve on the hose (that's what takes the water from the bladder to the bite valve, which is what you put in your mouth, bite and suck). It's a good system, but I wish the hose was insulated and the bite valve had a cover.
My other system uses and Platypus backpack (smaller, holds a two liter or smaller bladder and just a few other little things), a Dromedary 2 liter bladder and a Camelbak insulated hose with a cover for the bite valve. With this system, to hold the hose in the correct position (so that it's not flopping around all the time) I use a clip that I got at work and is usually used to hold name badges. It's a flexible piece of plastic that snaps to form a loop (that goes around the hose) and it is attached to a metal spring clip (that clips to the strap of my pack. Wish I had a picture.
I really like both systems and highly recommend them for anyone who is outside in warm weather doing just about anything (yard work, amusement parks, hiking, etc.
The frozen neck things from Sharper Image probably don't work in Florida because they rely more on evaporation to help keep you cool. And, in the summer in Florida, there's already too much water in the air (too high of humidity) for much of anything to evaporate (which is why I don't like the mister fans either, but I know many who disagree).
As for the original poster, if the kids are doing okay in school, I say pull them out and go when you want. My parents pulled my sister and I out for week long vacations at least every few years and we were better for it. We always had homework to take with us (try to get it done early in the trip, makes things a lot more enjoyable.) but I don't remember it being unbearable. In fact, one of my favorite family vacation memories was my sister and I sitting on the bed in a little bed and breakfast somewhere in the English countryside (I think it was outside of Bath), doing homework. I was a junior in high school, my sister a sophomore in college. She was taking calculus and taught me the basics of taking derivatives so that I could check her homework. My parents had pulled us both out of school for a week to take advantage of a great airfare deal. I still credit that trip and the European vacation we took the summer before to helping me pass the AP European History test (AP classes weren't offered at my school). I often learned more on the trips than I would have had I been in school. (But, again, depends on the kids. My sister and I could handle it. Not all kids can.)
If you don't want to take heavy school books, just photocopy the pages you need.
Sometimes the winter months can be really cold, and sometimes they can be pretty comfortable. 
It all depends.
