Been married 23 years, just last week. So my advice is this:
This is her first Christmas party at this job, you've only been married a year and this is this year's biggest get together for her job? If that's the case you HAVE to bite the bullet, sell the tickets or give them away and attend with the wife with a smile on your face the entire time.
It would look bad for the wife to have her new husband ditching the office Christmas party to attend a basketball game. Real bad. And, she won't live it down at the office.
Long happy marriages are all about love, sacrifice and compromise. In this case, sorry guy, but her good standing at work and upkeeping of a good working atmosphere appearance that she is in a good and happy marriage with a wonderful guy willing to give up basketball tickets to see his favorite team to go to a work party with her is more important than your seeing this game.
What I would do is tell her you'll attend but she'll have to make it up to you by going on a weekend trip to either Memphis, New Orleans, Dallas, Indianapolis or Chicago and go watch the Celtics with you there while making it into a romantic weekend vacation.