B.F.
I'm so sorry you're having to go through this! You all must be so anxious. It's good that you have gone through it yourself, at least you know what to expect. I'm sure you'll agree that the prep was the worst part of the procedure (or it should be! you shouldn't remember the procedure at all). I'm thinking that a kid might do better about the fasting--kids love jello! As far as the go-lightly junk-I recently heard that there are pills? That would be so much better then having to drink that nasty junk. So you might ask the dr about that if they haven't mentioned it.
That leaves the worst part, the diarhea. I can't think of any tricks for that part, it's just not fun.
I hope that things go as smoothly as possible and that it is nothing serious. Good Luck!