Heya--
I'm with you on the 'travelling is exhausting' thing. People who say things like "I really want to travel to lots of other countries!" completely perplex me. :)

You are extremely within your rights to spend your Christmas with your own family. Your mom is a grown lady. If she can't handle not having you around for a Christmas or two, well... that's a problem you can't solve. That's a problem for a counselor, or for whatever other sympathetic ears she has at her disposal. She certainly can't kill you over the phone. It may seem like she can, but really? You've got two young kids. You've got a busy life, a career that involves an extraordinary amount of effort, hard math, disappointment and long-range travelling, and anyone who'd hold a low-key Christmas at home with your kids and your husband against you is being so unreasonable that I don't even have words for it. You need chill time to function as a mother, a scientist, and-- yes-- even as a good daughter. Don't let her bully you into anything. She's had 30-odd years to prove that trekking many hours to hang out with her at a stressful time of year is a beneficial thing for you, and-- well, you are a smart and sensitive person, and if you feel like it's not worth it this year, odds are extremely weighed towards the fact that you're right.

Also! Are you planning on attending the AAS in Seattle in January? I'm going, so if you're there we should go grab dinner/coffee/tea/pandas/snowflakes.