1. Get one of the dispensers with the large jug.
2. Only allow the kids to drink at the dispenser so any spills are contained to a designated area that can be kept clear. Use small paper cups to further limit the amount of possible spilled water.

Those concerns were comically easy to address. I really expected it to be more about the kids using water or bathroom breaks to run out the clock and avoid the math practice, which you have to address on more of a case by case basis.