I had this dilemmas OP - I hate the whole thing and it makes me really uncomfortable, the lying and all the stress making sure they don't find out, and even worse when people use it as a threat to behave, or say you won't get presents if you don't believe. Ugh!
(And I'm not a fun sponge, and I actually don't mind Santa at all as a fun character - it's just how serious and pole-up-the-arse people get about "the magic of Christmas!" and "spoiling their "innocence"!!!)
But the thing is, everyone around your DC will perpetuate it, and it's a huge part of culture and if you try to "not do it" you'll have an even more confused child. You'll also find that many, many adults take it incredibly seriously and will hate you.
So, by the time mine were aware of Christmas I was going along with it, but I always tried to make it fun and silly rather than A Matter Of Utmost Importance That You Believe. I talked about Santa but in my head, without spelling it out, I was talking about him as a fun fictional character, just like you might talk about a witch or fairies. I never told anyone they had to believe in anything. We did the whole mince pie and carrot thing etc and stockings from santa (not main presents) and the kids enjoyed it. But by age 5/6 their logical minds set in and as soon as they questioned it I didn't lie. i said "it's just a fun christmas story" and we carried on doing all the stuff (still do!) but they know "santa" is really me. Teenager still jokes about Santa coming and that Santa should remember not to fall asleep before doing the stockings etc. I think I've made it as fun as possible without feeling like I've deliberately misled them.
There is the issue of them telling other kids, and I did tell them not to but I suspect they sometimes put their foot in it. But kids do tell each other, that's how it goes. Then their parents start with the "Santa only visits those who believe" and try to spin it out. IMO if you've got to 9/10/11 and still believe (SEN aside) then a few home truths from your peers are probably a good thing.