Can whitening strips be used with front crowns?

Yes they can be used, however, the crowns will not change color.  If the natural teeth are darker than the crowns, you should get some improvement in the uniformity of the color of your smile.

You are correct that the crowns will not whiten during the process.  The crown finish should be unharmed using traditional whitening products and only the natural teeth will be whitened. 

Whitening strips will not work to whiten crowns, they can be helpful if your teeth are darker then the crowns to balance the color of your teeth.