R.J.
We ponied up the cash for the mattress protectors that are "celled", which allow air to pass through, but not water. They're terrycloth on one side and rubbbery "stuff" on the other. You can breath through them just fine, and you skin can "breathe" as well, so you don't wake up wet.
Sleeping on a normal waterproof protector even *I* would wake up in sweat, and my son would wake up soaked (sleeps hot like your boys). These ones, however, everyone wakes up dry.
They're expensive as all get out. $150 for my son's double, almost $250 for the king. And worth every penny.
We got them through SleepCountryUSA. I looked online but they don't have an online store anymore it looks like. Perhaps something local to you would have something similar.