I can't call the elderly or in-laws by their first names, we're used to address them with po but here there is no po so just address them using the uncle, auntie, dad, mom. In my opinion.
I can call my boss with his/her first name bec when i was still in the Phils we can call our bosses by first name. I guess it depends if the person accepts it and/or if you're working in a company where it is considered a norm.