There is absolutely nothing wrong with it and I am so pleased, though somewhat surprised, to see some Catholics here agreeing. Because from my experience it’s the religious “right” and other Christians of a conservative persuasion that make a fuss about there being a “war on Christmas” in their minds. There is no such war.
I have in the past sent cards with “Merry Christmas” on them. To those whom I knew celebrated Christmas. This year the cards I sent said “Happy Holidays” and when I ran out of those, I opened another box. Those said “Seasons Greetings”. And I wrote Merry Christmas inside. Had I sent to someone of the Jewish faith, I’d have written “Happy Hanukkah”. If you call my phone right now you will receive a voice mail greeting that begins with Hi and Happy Holidays! I recorded it for the time period Thanksgiving-New Years. I live in a diverse area, racially, culturally, and religiously. During Ramadan, I’ve wished my Muslim neighbors a blessed Ramadan. At Christmas they’ve been known to wish me “Merry Christmas”. I never have understood the hoopla either.