Do you have a mom and baby who can nurse on camera?
Some ideas off the top of my head. . .
I was thinking have mom sit on a toilet in a public restroom (probably have to get some kind on permission to take a camera in there) nursing looking disgusted and uncomfortable while there are toilets flushing in the background. Then ask something like "Is this where you want your children to eat?" Then show mom and baby peacefully nursing somewhere in public.
Or you could reverse the scenes and go for sarcasm. Show mom peacefully NIP, smiling at babe, people minding their own business, then say something like "How could she do that in public, she should do that in private!" Then show the bathroom scene and say, "yeah, that's better." (alternatively you could have a security guard come up and tell her that she's not allowed to nip and she needs to go to the bathroom, then you can bring out whatever laws your state may have protecting nursing moms)
I really think most people are much more freaked out by the idea of NIP than the reality. They picture some weird militant hippie mama waving her naked boobs defiantly around all over the place. So I think images of moms niping as just a part of their normal day w/o all the imagined fuss are very powerful.
What a neat project! Is there any way you could link us to it when you finish it?