I asked mine if they still wanted to “play the Santa game” and they did, so we do.
I go through all the usual motions, and still talk about Santa bringing presents. You’ll have to see if Santa will bring that etc. I refuse to be drawn on where the presents might be hidden, insisting that they come from the North Pole on Christmas Eve. It’s actually more fun now that they’re in on it. I was also stressed that I’d slip up and I’m a terrible liar. It’s so much more fun now that it’s tongue in cheek.
They pick things for each other’s stockings and I’m thinking that this year I might add in stockings for me and dh and let them fill them for us.
We only started elfing about when they stopped believing. It added a bit of fun without any real pressure to remember to move him. Dd set him up herself a few times.
They still wanted to visit Santa which surprised me, although the one we go to see is absolutely fantastic. He makes me doubt the non existence of Santa! When they stop going I’m going to have to borrow kids or go on my own 
I’ve also included them in the charity side of Christmas. Before they would have been confused by the idea of buying poorer children gifts because obviously Santa looks after that, but they took a big interest last year. We also filled shoe boxes for the homeless. We’ve always emphasized giving at Christmas in the form of making gifts for relatives or sending a hamper of art supplies to the children’s hospital but it was nice to see them becoming a bit more socially aware.
I was devastated when they rumbled Santa, particularly as they were so young, but it’s not been as desolate or bleak as I imagined. It’s just a different kind of magic now. And in all honesty, I prefer not carrying the burden of secrecy anymore.