Jobs in science, engineering and technology will nearly all require a working knowledge of Linux and the open source applications surrounding that OS. Teaching a standard desktop and office suite really has little value in the long term.
It is very likely that all but the most menial jobs will require some level of programming, and most of that will be on top of open source applications and platforms.
I'm not sure about the aggressive advertising. Girl Scouts don't diss Oreo to sell their cookies. They rely on family to buy a couple and maybe a bunch at the office, or retail entrance. By the way, GS cookie margins are larger than the 10% you're suggesting.
In many ways what you are suggesting is One Laptop per Child in a commercial way. Or the Raspberry Pi project with a established marketing arm and a built in customer base. The majority of scout families will buy an inexpensive computer each year so kids don't feel bad. Since you don't want to deal with support and limit defective returns (including user inability to understand the OS), this will have to be an appliance with conservative specifications.
I'm not saying it can't be done. A Linux based computing appliance in the $50 to $100 range sold by Girl Scouts could easily move two million units. You take pre-orders (like the cookies) and manufacture to demand. I'd go even further by having the scouts charge for and provide support and education. What better way to get girls involved in tech by making it part of their responsibilities as scouts?