It's time for our blended family Christmas.
The turkey is ordered, the tree is earmarked, and the day will unfold with the usual landmarks: Christmas stockings, the Christmas morning church service (where a live, interactive Nativity play takes place), then a quick walk before we head home for lunch.
This is the classic Christmas dinner with all the trimmings and crying out to be enjoyed by one big family.
I am really looking forward to it - and so is my husband. This year there is a sense of relief that no one is being left out.
A few years ago, I would not have ever bet on this turn of events. When the children were young (they were 14, 12 and seven years old when we split), Christmas had so much emotional freight attached to it.
I even found that a splinter of sadness pierced the joy of the "on" year celebrations as I began to anticipate the loneliness of the "off" year. I imagine it was the same for my ex-husband, who hasn't remarried.
Now, with one son aged 28, the other 25, and my daughter 19, the pressure of slicing family life into "his" week and "my" week is off.
My sons both live overseas, and have done so for the past three years, so all of us are keen to spend time with them. They come back at Christmas and family is the priority.
It's amazing how much of the antagonism of divorce falls away simply because you both miss your grown-up kids.
Given that there is so much intensity of emotion around Christmas, there is something soothing about the rituals a family puts in place to celebrate it.
Whether it's playing charades, dressing the pug up as an elf or watching the big Christmas Day film, it comes with an expectation of laughter and ease that sets the mood of the day.
Similarly, the amazing effort that goes into preparing Christmas dinner is a shared experience, rich with forensic detail that means everyone can have a part, no matter how menial.
Whether you are one of the little cousins peeling sprouts, a teenager pouring too much brandy on the pudding or Mum wielding her powers of persuasion over the turkey to will it to be ready on time, you are all involved.
A jigsaw puzzle of Elvis Presley is waiting for the right combination of family members who want to sit around piecing together his famous golden suit. Such time-honoured rituals with a twist are great for healing old relationship rifts and for opening the way to new shared memories.
Of course, seeing the children is the priority of our Christmas Day.
But also, there is an important acknowledgement of the different generations who all come together infrequently in a far-flung family. This year we will have 14 at the table, and the age range hits just about every decade up to 90.
Christmas is tribal, clannish, and a time to set aside differences. After all, people come great distances (in our case, sons from Berlin and Beirut, and their uncle from Barcelona) and everyone makes a huge effort, and that in itself is worth celebrating.
Even when my ex and I spent our Christmases separately, my children always wanted to see their younger cousins on both sides, whose adorable and hilarious utterances are favourite family memories.
Whether cousins were available or not, we would also include close friends, single friends, families or parts of families who were, like us, lopsided post-divorce, or bereavement or just about any circumstance that doesn't fit the Waitrose ad come true.
There is a parallel universe in which the recognition of how tough Christmas Day can be brings gallows humour and lots of tearful gratitude.
Gathering up various individuals and families was what we did to magnify the Christmas experience in the years I was with my children. The alternate years, I was sometimes one of the gathered, sometimes not. Planning Christmas when I didn't have the children had an element of playing musical chairs. Searching, furtively at first but with increasing panic, I would make indirect inquiries about what my friends were doing.
There would be a discussion about a holiday or a yoga week, but it rarely came to anything: too expensive, too difficult to coordinate dates, too painful to commit to doing something so different when the maternal magnet tugs you towards family, home and hearth.
Suddenly, I would look round and it would be only a few days to go before Christmas and I would have no plans. Terror struck. Blind panic.
I remember one year, an extra cold Christmas, icy roads made going out in rural Norfolk, where I live, treacherous.
Instead, I lit the fire and retreated to the sofa with my duvet and many films to watch, many Chocolate Oranges to eat.
I don't know if I would label it "the worst Christmas", but I do remember a lot of hugging the dog and tears wiped on her fur.
It was actually saved from utter gloom by the arrival of a fire engine, when I thought I had set fire to the chimney.
No damage, but I had a cheery cup of tea with the firemen, offered them Christmas cake and felt I was taking part in a rom-com movie.
(Take note anyone who is contemplating this kind of Christmas: Stanley Kubrick's multi-Oscar-winning period drama, Barry Lyndon, is good and long, so is Gone With The Wind, and thank God for the invention of the box set.)
I have spent other challenging Christmas Days with close friends, on a plane and driving up and down motorways.
Girlfriends have included me in their family Christmas, and it is fascinating to be an onlooker rather than a central character.
I have been granted an insight into what it will be like to be an older relative, as my girlfriends and their husbands tussle with the personalities in their families while I am on the sidelines. Everyone is always friendly, but I know I am not essential.
Of course, meeting my new husband and having another person at my side through the non-family Christmases has been a huge bond between us. His children are always with their mother for Christmas, so he and I have experimented with many versions of Christmas together.
We have had a strange extended Sunday lunch at a pub by the sea, and other years have cooked our own pheasant for two. One year, he and I even drove across many counties to have Christmas lunch with his daughter, his ex-wife and her husband.
We have also been away, to Rome, where it poured with rain and we queued outside the Vatican for a damp and crowded audience with Pope Francis.
Last weekend I made a Christmas cake. It's trussed in a tin on a dark cool shelf, but it comes out every few days to have brandy dribbled into skewered holes.
This is something I do every year, whether I am with the children or not, as there are always visitors, and the children like it when they come back after Christmas. It is my own private ritual, and the smell of it baking is the sensory opening of the Christmas season for me.
This year, the experience of sharing Christmas with the extended family will be exciting and fulfilling. There are personalities enough to make sure there are no awkward silences.
There are also absences, sad gaps, such as grandfathers. An annual get-together no matter what season it is, is a solemn reminder that nothing stays the same.
In time my children will head off to the home of their partner's parents. Then, probably, a stage will come when they begin to have their own families, their own Christmases.
Suddenly, one day, I will wake up and find myself hoping to be included by them, and life will have come full circle.
I might then look back at the alternate years of their childhood Christmases as a luxury. In the meantime, though, I don't want to take anything for granted.
All of us, under the tinsel and turkey, have moments of loneliness over the festive season. It isn't possible to be a part of a family and not know loss. It is the counter-balance to love. Christmas throws this into stark relief.
All of us know how much it matters to show people they are not alone. Christmas is about the joy of giving and sharing.
