One of the many Filipino urban traditions that my in-laws practice whenever a visitor greets my cousin's baby is to say "pwera usog" or "pwera bati". Do you also practice this?

Yes! that is usually the practice in the province. Actually I don't believe in it, but there will be no harm done if you practice it, right? So I just let my grandparents and other people do it especially when we go out of town. I find it weird but you have to respect Filipino traditions :)