regarding pregnancy, I HAVE taken SA to tolerance, quite frequently. Sometimes that is 20,000 mg (20 g) other times, it is much much higher to the point where I haven't hit tolerance during the day. I really don't keep track of how much I take, I just take to tolerance. Anecdotally speaking, I started this during my last pregnancy (2007-2008) and had a remarkably easy pregnancy, birth and a very healthy baby. I'm currently pregnant now and have, several times in the pregnancy, found it necessary to dose to tolerance.
Regarding children, you can look at
www.vitamincfoundation.org for recommendations and here is the one from orthomolecular.org The below is preventative and maintenance schedule. (Some people I know only dose to tolerance with vitamin c when ill.)
For children the recommendation is 1,000 mg (1 gram) per age of child leveling off at 10,000 mg (10 grams). So a 1 year old would get 1,000 mg (1 gram) per day, a 2 year old would get 2,000 mg (2 g), etc.
I know that
www.vitamincfoundation.org also has some dosing requirements posted. From what I recall, there is a also a comparison chart on there of the different requirements given by various organizations and researchers.