For glass and plastics, any window cleaner will remove the film.

For cloth you may be looking at a steam cleaner like those used for
household furniture and carpet [or a smaller equivalent]. Or you may
want to talk to a car detailing shop.

I know there's also a carpet cleaner in a spray can, normally found at
auto parts stores I think. I've never used it so I can't testify to
it's effectiveness.

In the meantime you could ban smoking in the minivan.

As for the small children, you can just toss them in the tub.