Question:  I just renewed my kids passport and the I-94 which he received is valid till his old passport expiry date which is coming in January 2018 but visa is valid till June 2018. Now I want to make changes to his I-94 as per new passport.

Answer: You may want to take the new passport to the CBP and find out if they will stamp for the remaining validity period. However, it is more likely that CBP will not do that and will either require you to leave the country with your child or extend the status by filing another I-539 while in the country.