Sophie, I had to chuckle about the "discussion" comment your h made. What's there to discuss? Thanksgiving comes once a year and you and your children have the day planned. Once you clarified for him that you were going to be home and if he was interested, he settled down again.
Now, if he comes over, no discussion about the divorce. This is to be handled by the two lawyers and for one day, keep things simple and light, if you can. Act as if. However, do not be surprised if he doesn't show up. They all come up with excuses every now and then not to come over. If he doesn't, that's okay. If he does, be on your best behavior and know that you are up for the Golden Globe Award for Best Actress.
I do hope that he'll consider coming over, but it shall be interesting to see what he will do.
Please take care of yourself.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.