In Mexico, polite interactions often include elements of warmth and personal connection. Among the options you provided, option A—stopping and chatting for a minute to ask about the other person's family—is generally considered the most polite. It shows genuine interest in the other person's well-being and fosters a sense of camaraderie.
Option B—kissing the other person on one cheek (a customary greeting) and then continuing to walk—also demonstrates politeness and affection but may indicate a more brief interaction without the follow-up conversation about family.
Option C—waving and saying hello while continuing to walk—is polite but might come across as more distant or casual than the other two options, as it does not encourage further interaction.
Overall, if you're looking to be seen as particularly polite and respectful in Mexican culture, taking the time to stop and engage in conversation (option A) is the best choice.