Stray Kittens- What should I do?

I live in an apartment complex. A neighbor took in a stray cat and it gave birth to 6 kittens... but they let them out all the time. In fact, the mom and all six kittens are playing in a bush infront of my patio right now. I worked for petco for a long time and have sat through a bunch of lectures on how susceptible cats are to disease and why you shouldn't let your cat outdoors. Especially with teh kittens, I am worried about what people might do to them as they are not obviously claimed (no collars or anything). I don't know of anyone who will take them- maybe a shelter?? But would calling the shelter be offensive to these neighbors? I'm not sure what to do.