Lala,
I just finished up as the PTO president at my duaghter's school for the last two years. We had such a "brigade" at our school, and you should tone it down or you will be "that Mom" even if you have company. It was especailly difficult to deal with them because our district has already been responsive to reasonable efforts to improve the food choices our children have at school. That was not good enough, and they wanted to ban all white sugar from every classroom party and birthday treats. Don't go there, you will be driving the crazy train, and you don't want to.
Our district had a well run bunch of like minded parents who went about making things better in a good way, the "brigade" came into the district after these people made good progress, and still found issues, because at some point, this crusade becomes unreasonable, so be careful. About 6 years ago, the reasonable bunch found each other and mangaged to make positive changes. They approached the board of education in a very business like way, and made a proposal (in the way the board hears requests- a copy of that policy is avaliable from your school district and you must play by their rules) that all the sugary drinks, candy, icecream, etc. be removed from the vending machines, and that healthy alternatives be added, like water, juice, or low calorie beverages, and nuts, or jerkey replaced the candy and chips. At the same time, they asked that the snacks available at the cafeterias include healthy alternatives. There are only a few items that could be viewed as "bad" available now in our cafeterias, and the vending machines are out of all the elementary schools completely, and the only ones turned on during school hours at the high school and middle school contain only healthy choices. There are a couple of machines with junk in them that are only turned on after school hours, so our kids cannot choose coke and chips for lunch anymore.
If you were talking about a PTO/PTA fundraising sale of such items, this would be a once in a blue moon kind of offering, in most cases, but this sounds like it is a regular cafeteria stocked item, which you have ultimate control over. In the long run, you decided what your child eats, even at school. If you do not like what the cafeteria offers, pack her lunch and do not give her money to buy things that you do not approve of.
In my understanding, the overall content of a regular school lunch is regulated by federal guidlines of fat, calories, protien content, etc. School cafeterias can offer the extras, and what is stocked for sale in cafeterias, as well as the availablity of vending items, is a decision that is made at the district level, under board of education control. You can do something to change that, but if you don't want to come off as "that Mom" quit blogging, ranting, and talking about your outrage, and tone it down such that you can attract more like minded (and maybe even much less outraged, but more middle of the road, individuals) and find out how to approach your board of ed. If you are not "that Mom" when you organize your group and present to the board, they will take you seriously, but if you are, you are dead in the water.
I can tell you though, if you say something to your principal, the PTO/PTA, or your cafeteria workers, or spend time ranting about it at school pick up, you will be "that Mom" and we will see you coming and dread it. None of these people has anything to do with the issue anyway.
M.