teenytiny,
I'd recommend starting educating your children about the disease while they are young and more willing to listen and absorb what you have to say. Not to freak your kids out, but just to prepare them for those times when their friends want to get high or drunk with them.
I have been pretty open with my daughters about taking care of themselves. I am disabled, due to a brain injury, so they've seen and dealt with the consequences for themselves. I'm therefore pretty darn strict on wearing helmets and taking other necessary precautions to prevent TBI. I sometimes go a little overboard on my worries about everything that could happen to my girls ~ but I'm trying to stay on the positive side with them.

Best wishes to you!