I also have a very small family and sometimes feel sad my kids have never had a big family Xmas, but TBF, they can be a nightmare. And nothing nicer than being able to chill in pyjamas Xmas Day.
A few ideas for traditions:
Do lots of Xmas things during December to make it feel special. The advantage of having one child is you can more easily afford things that’d be expensive for more than one. Trip to pantomime, light shows in parks, Xmas fayres and markets, ice skating, Xmas cinema trip. My Nan and Great Aunt used to take their kids every October half-term for a big day out to the shops, looking at toys and visiting Santa displays. Then, while they were having a drink, one would pop back and buy the favourite toy they’d seen. Though presents can be ordered online, it’s exciting for kids to look at toy displays and you can see what they like most.
Meet up with friends in December before they’re with family. Go to some of the above together, so your son can be with other kids. Invite them round for the evening to play games. Meet for winter walks and hot chocolate. You should have chance to make more local friends with kids once your DS is established at school and in clubs.
Start traditions of Xmas baking with your DS. My DSs still love baking. We have a cardboard template for a gingerbread house we use every year. You can make biscuits to decorate the tree. Or even Xmas cake and Xmas pudding on stir up Sunday, mince pies etc. Tons of ideas online. Decorate boxes and deliver some to your next-door neighbours and invite them to pop in for a cuppa over the Xmas season if they’re at home. It’s great for kids to know neighbours well.
If your son makes tree decorations/crackers at school, keep them and write the year on the back, however rubbish they are (makes them funnier later). Keep anything people give him in December that can be hung on the tree. Little cars, teddies etc. We even have a random bauble a waiter in an Italian restaurant gave my son as a toddler. Then, every year, preferably as part of a special day out, take him to a shop with lots of Xmas decorations and ask him to choose only one tree decoration for himself. Write the year somewhere discrete. Each year, when you decorate the tree, you can talk about the memories of him making or getting the decoration. And you’ll have a lovely, growing, eclectic mix of meaningful decorations.
After all that, by Xmas Eve/Day, you’ll be glad to snuggle up just the three of you. I suggest having brunch after opening presents, then a nice walk around midday so he can let off steam (we used to drop cards into neighbours Xmas lunchtime cos I’d have only just got them written!). Then come back and cook your dinner for about 5pm. If you’re cooking all morning, by the time you’ve eaten, it’s too dark to go out and the day can feel a little depressing and kids can get cabin fever. In mid-winter the best part of the day is midday.
Enjoy!