I call both my parents and my in-laws by their chosen grandparent names any time LO is within earshot. DH usually does the same, though sometimes he will say Mom/Dad.
Likewise, my parents call my husband & I Mommy/Daddy anytime LO is around.
My in-laws don't refer to DH & I as Mommy & Daddy. They might say to her, for example, "Take that to your mommy," but if they are calling us by name it is our first names. I am even called "Auntie Danielle" on occasion! That's what the nieces and nephews have been calling me for 6 years so I understand the mistake, though I always correct it.
Just curious what is done in your families! I think I am a little more sensitive to teaching LO the "correct" names because I grew up calling my stepdad by his first name, and therefore my younger half-brother never learned to call him Daddy because he didn't hear it. He calls him by his first name like my brother and I.