Thinking about it, depending on the age of the little ones, I wouldn't show things like Food Inc, unless you want some pint sized vegetarians on your hands.
I would however, start right now and look for a local FFA or 4H chapter, and encourage your kids to get involved - and you get involved...
I grew up on a farm, we had chickens, ducks and geese. Our chicken came from our farm. Our beef came from "Uncle Dick's" farm (family friend). Our pork came from our neighbor's farm. That's where meat came from.
I grew up eating that meat, and when I got older and we started eating store meat...