Speaking as an ABC who grew up speaking Sei Yap, I would feel uncomfortable addressing them as "a mu" or "a vak" (auntie and uncle in sei yap) unless asked to address them as "a mu" and "a vak." Of course I'm older and my family's been here a long time so we are fairly conservative. I just remember my mom commenting that 1 particular guy was very well taught and well mannered in addressing her as XXX tai (Mrs. XXX) while others addressed her as "baak mou" which she took to be a little too familiar.
Did you ask them how they would like to be addressed? This would probably be the safest route not to offend anyone.
Did you ask them how they would like to be addressed? This would probably be the safest route not to offend anyone.