Validity of I 94 for H4 visa holder

Husband has approved I 797 petition valid till 2015. Wife and 5 year old child come to India in october 2013 . and return after stamping to say Nov 2013

Child’s Indian passport expires in May 2014.

In such a case what will be the validity of I 94 for child ?

Does this depend on discretion of Port of Entry officer or there are definite rules ? Will the child be granted I 94 validity only till validity of passport or till validity of petition?

AFAIK, your stay cannot be beyond your passport expiration date. I suggest you renew your kids passport before you enter US.