Why go to Mexico? Your parents is Canada perminant resident
their B1/2 visa are mutiple 10 years entry, if they do want to stay in US longer, they can file extension. Even re-entry to the US to get the new I-94, they should go to Canada.
Your choice is not in good logic. US board officials may also think so.
Your choice is not in good logic. US board officials may also think so.