First of all, update that title. It gives a really bad vibe.
As for the question, don’t try to be a “good uncle”, don’t pretend to know stuff the kid does unless you know it. Ask your friend how to approach the kid. I’m almost sure all tips you get from the random people from the internet will be useless or confusing.
None, you should appreciate people in your life on a daily basis and not because some holiday tells you to do so.