It's your first sentence above - DH wants to drive to his parents the day after Christmas. He's not breaking the "which family are we celebrating Christmas Day with" agreement, but he's adding in the 26 hours of driving again this year. I was looking forward to staying home.
I am relieved that some of you empathize with how dangerous the roads can be in the winter, in addition to DH's habit in driving like a Formula 1 racer.
After posting with everyone yesterday, DH and I had a calm talk. We agreed to let this argument slide. I was operating under the belief that I'd only have to travel during Christmas time every other year. He believed he was honoring our agreement that we'd spend the actual holiday at home with my side of the family, and didn't see why he couldn't slip in a trip to his parents also immediately after. We'll discuss at a later time what exactly we agree to do for the holidays from here on out.
Our mutual solution:
I'll travel to DH's parents this year, the day after Christmas, if he drives more carefully, no more 90 mph driving in the winter. He's offered to cancel the trip to his parents if the weather turns bad.
Whew, we made it through. Marriage is not for sissies.