I can relate to that same situation, regarding passing gas in an area among peers, and using the same toilet. I think a lot of other's can relate.
NoDayButToday has a good suggestion, which I agree. I had also asked for permission to use the "Personnell Bathroom" during my school days.
For years, even after school, I had held on to my gas and stools until I made it home, and after a while realized the fact that I have to pass it and stand up to whomever may challenge it.
My first thought is that because it's a bathroom, that if anyone commented to me while I was in there, I would just say "It's a bathroom, right?"
I'd go outside, and pass gas, making sure no one (Like my wife) is down-wind. (My wife and I joke about it--mostly because on our first date, she was the first to pass gas!)
She said it's unhealthy to hold it, and I agree; fewer stomach aches have come because I wouldn't hold it in, and just let it pass.
Some suggestions that I have found to help is to flush just as soon as you pass a stool. I look at it as "Not giving it a chance to breathe"!, also if there are windows and vents, to open them. I wouldn't reccomend it for a nine year old, but a flame will burn the methane and cut down the smell as well.
The reason for the fowl smell is related to the remaining protein in the stool (from what I heard). If your child still has oil in the stool, it'll add to the smell, and that's when diet and enzyme adjustment is necessary.
I hope this helped, some I had to learn as I went along.
