My SIL and Bro are having a similar hill to die on re: traveling at Christmas. Family tradition has always been that we get together at one house with Mom's side of the family (Dad has very little family living). Bro and SIL are always a bit late, even when the drive was only about 15 minutes. (At max, it's 45 minutes so we're not talking multi-state trips here.) Now that they have kids, SIL wants to do Christmas morning at home with just their immediate family, which makes perfect sense.
Mom, however, didn't quite get what SIL was getting at, at first, and was trying to figure out how that would change the whole family get-together. I said it wouldn't. They're welcome to spend Christmas morning at home together, and I (single, childless) am still planning to join the rest of the family for Christmas morning as usual. As we will also have a small Christmas celebration with Bro, SIL and the kids separately anyway, it's not like we're not going to see them over the holidays.