A trans parent would likely still want to be called “Mom” or “Dad”, I assume. At least that’s the case with the few trans parents I know.
Parents don’t usually use “daughter” or “son” as pronouns, so I don’t think it would come up with non-binary children.
Do children of non-binary parents call their parents by their first name? It seems unlikely that they say “Parent, may I please have more screen time?”.
Show some respect.
It’s a convenience store/deli/sometimes gas station, and it has the best Thanksgiving sandwich you can order, pay for, and pick up without a single word to a human (and usually in less than 5 minutes).
My humblest apologies!