So they will be at your house Xmas evening right? That sounds good.
I am a DIL so if your son did not say anything on plans, then DIL made the plans since he never did.
I am the same way with my husband, if he does not tell me anything about plans, then I make the plans with my family. I don't rule the house we both share in decisions, however, he is a guy, so he will not think of the "holiday" gatherings.
It is not that I don't love his family, but they never set a date until the very last minute. For the longest time we always went to my side of the family for the holidays then to his the day after. The reason was because everytime I would ask him about what his family plans were, he never knew or bothered to find out, so I would always committ to my side.Now he had the option of going to his side if I had already committed to my side. However, my side makes plans for the following year at the present gathering. Who ever has to host it has a year in advance to get ready for it...It has worked out well my huge family. I have 15 sibilings....
Now in the last 5 yrs, his family has made plans with dates, so we have been going to his side, then my side.
Now what you can do for future holidays is set a day & when you will host Thanks/Xmas. And let your son know..
He is a guy so he will leave it up to his wife. Your DIL just made choice if he never spoke up. My husband will tell me if we are going to attend his side so I know not to make plans with my family.
This Xmas, my side will have it on Dec 25, I will host Xmas for my husbands side on Dec 23 at our house.
Now if you want to have something for say Easter, then plan it now and let your son & DIL know...when they come over for Xmas.