Here’s a hilarious (and largely accurate) article to help you figure out how to fill out your Christmas (or other-holiday-of-your-choosing) card.
Q: What if my last name ends in a Y?
A: Add an S. Do not add -IES or an apostrophe.
Merry Christmas from the Murphys.
Q: What if my last name already ends in an S?
A: Add -ES. Do not add an apostrophe.
Season’s greetings from the Simmonses.
Q: What if the end of my last name normally functions as an irregular noun?
A: It is not irregular when it is part of a last name.
Happy holidays from the Hoffmans. Warm wishes from the Wolfs.
Q: What would adding an apostrophe do?
A: It would hurt Tiny Tim make your last name possessive.
Go read all about it: http://www.slate.com/blogs/browbeat/2014/11/25/how_to_make_your_last_name_plural_on_holiday_cards_and_avoid_apostrophe.html?google_editors_picks=true