This Christmas element and the fact that it's traditionally a time to visit family is confusing the issue.
Either you can afford it or you can't. Don't let the time of year muddy the discussion.
As adults, we can all seperate out what we'd like to be the case (able to visit relatives), vs. what actually is (you have a finate income pot to distribute).
You need to sit down and work through the figures with your DH and come to a comprimise based on that.
Whether you want, or he wants, to visit relatives, is completely moot. The first and foremost question is whether you can afford it, based on all of the unexpected recent bills that have come in.
Once the answer is 'yes' to that initial question (be it wholly, in that you all go as a family, or partially, in that you can afford for him to go alone)... then, and only then, can you start to address what people want to do.
In summary, I feel you're focusing on the wrong element here, as are many of the responses on this thread. Time to step back a little and take some emotion out of the decision - you won't (and don't have a right to) dominate the decision based on opinion alone, but you do have the right to veto this visit based on the household income on top of your opinion.
that's my view, anyway.