My L1B visa expired February 2014, and I got an extension on I-94 till January 2016. I have a new petition valid till January 2016. My son was born here in the US August 2013. My wife also has the same expiration dates. Can my son and wife travel to India for 2 months and come back? Will there be any problem in stamping in India?
Your extension on I-94 allows you to remain in the USA. I believe when you leave the USA, your I-94 will get an exit stamp. When you leave the USA your I-94 is over, unless it is a short-trip (up to 30 days) to Mexico, Canada or adjacent islands, in that case they will re-validate your existing I-94.
Leaving the USA for any other country, like India will result in your I-94 showing an exit stamp. When you return they will have to issue you a new one, however you will need to have a valid visa to get one.
Without a valid visa they probably won't issue you a new I-94, and on the Indian side you probably won't be allowed to board the flight.
Your son will be allowed to re-enter as he should be a USA citizen by birth (you may need documentation to prove that). Your wife will not be allowed back in without the appropriate visa.