I don't think I'm being particularly selfish that over a 6-7 day stretch, the one day my husband isn't at work for 12-14 hours… I'd like us to have some quality family time together
You are. Yes you are! This is the exact definition of selfishness. Everyone else, including you husband, wants to go to the in laws. They consider this quality family time. The children are not desperate to spend more time with your husband (or you for that matter, sorry) to the exclusion of seeing and playing with their cousins at Christmas. Your husband wants to immerse himself in his extended family Christmas, warts and all.
We all view Christmas differently. Some people think of it as tradition, focused on children, nostalgia, extended family and season of good will etc. Others see it as a time for self care and relaxation. Neither one is right but I suspect you don’t share the same view as your husband and children. Would your Christmas at home involve full dinner and traditions or would it be more open presents, stick a movie on and pizza tea?
The problem is surely your husband’s working hours, rather than anything to do with his family. It’s unfortunate that his job involves long shifts/working weekends etc (hospitality, care, retail?) Is it possible that as his career progresses he may be able to have more control over this? If not, this situation will repeat itself year upon year.
Sort out with your husband how you each want Christmas to look going forward. If it is very important to you to have him around more over Christmas, look at how his employment can change to accommodate this. It might mean a drop in salary or loss of flexibility elsewhere.