First of all, your ped seems a little misinformed about the use of vitamin C and toxin-mediated illnesses, but it's not surprising as most doctors don't have a clue. If it is actually pertussis, hitting the right dose with SA will make a huge difference in reduction of symptoms.http://beyondvaccination.com/showthr...ral-management
I wouldn't have believed it, if I hadn't experienced it firsthand. It was the difference between my kid coughing every few minutes all night, whooping, and throwing up, to sleeping most of the nights peacefully and no longer gasping for air.
Bowel tolerance isn't so much a calculation as it is observation. You dose with SA until they've got loose (and frequent) stools...that could be 4g, 5g, 6g...once the symptoms are under control, you can lower the dosage.
And I've only used SA. I can't imagine trying to get that many chewables into my kids. The SA is in a powder, 1/4 tsp is 1g, so it's pretty simple to add it to juice or applesauce.
As for quarantine, it depends on if you're LO is on abx or not (I saw that you didn't put her on them)...The general consensus is 1 week if on abx, 3 weeks if not (I got this from the CDC site). We did not use abx, so we kept our little one home for 3 weeks.
Finally, as for telling, would you want to know if your child had been exposed? I probably would so I could prepare. You know your friends best, so how you go about it is up to you.