On the night of bedikat chametz I will be at a house where the family is not religious. How do I do bedikat chametz if there is chametz throughout the house and none of this chametz belongs to me! I will not be there for Pesach, only for that night. Do I just search my pockets and bags?
You do not need to check the house for chametz, because it is not your house, and you will not be there over Pesach. However, although the family is not Orthodox, you can still advise them to pool the chametz together in one place, and to sell it — you can even perform the sale for them over the internet. Do it ASAP if possible.