
I've been asked this a lot this year, because we seem like the sort of family who wouldn't do Santa.
(I always say Father Christmas, because we do both Father Christmas and St Nicholas.)
This year has been really interesting, because it's the first year they realised that he doesn't visit children who don't celebrate Christmas. And that was a thing I thought would be hard, but it turns out not to be.
Firstly, I never say he comes only to good children. I never use it as a threat, or a reward. It's just that Father Christmas is a Christian overflowing with joy in the Incarnation, that he wants to share his joy around, and he does that by giving presents. That's similar to how I describe birthday presents - I'm so happy that there's you, I wanted to give you a physical representation of that. Father Christmas loves people, a thing we all aim to do, and he loves Christmas, and so there are presents. He also is super respectful, and knows people, so he knows which children don't celebrate Christmas and therefore shouldn't be given presents.
This that I thought was going to be hard, turned into a nice easy way of discussing how it's rude to force your traditions or values on other people - it's OK to offer and share, but you need to listen too.
Then, as they get older it becomes less about the hypothetical physical man, and more about the feeling of joy, the feeling of exuberance and love and presents as a symbol of love, and a metaphor for sharing the good things. See, that's the kind of Father Christmas I believe in, so I definitely don't feel like that's lying. But there are different types of reality - the physical and the metaphysical and the emotional, and they're all valid and all worth talking about.
(Oh and the thing about going to bed early? Um. I sort of know it's not true but maybe I forgot earlier and told them it was a myth, which I always assumed as a child. We'll go to bed after Midnight Mass as normal.)