If it was me, I’d say do his birthday, because he’s not your father. There’s no “Son’s Day” on the calendar ... that’s why people have birthdays!
Anoreth emailed from some unknown location within 60 miles of the coastline of some fairly civilized country. At least we know she’s still afloat. She expects to get her orders for Gunnery School at some point during this cruise, and one she has the paper in hand, she can be sure she’s going, barring a man-overboard - girl-overboard - incident.
She’s going to collect some more interesting nicknames.