My family was religious enough that they made it super clear that Santa was fake. Us kids still got little gifts “from Santa,” but they were of the stocking-stuffer variety. All other gifts were from specific people. As a kid I liked getting stuff, but the more important thing about the holiday was spending time with family, and them showing their love. Gifts was one way to show, but spending time, preparing meals, and just being present without worrying about other life issues also did it. It is the thought that counts, but you have to show that you’re thinking about them. Honestly, your kids might appreciate not having to pretend they still believe in Santa. As other people have said here, don’t catch your kids in the crossfire. If there’s something they’re really looking forward to, get it for them, but label it “from Dad” or Mom and Dad if you’re feeling generous. If they don’t have their hopes on something, a trip or experience might be good. Not sure what experience fits both a 6 year old and a 12, but I assume you know your kids better than I do. As for the rest of your family, they can stick it. They don’t seem interested in participating in the holiday, so don’t include them.
I find 2 per PC is my useful limit. Which means my current 5 isn’t quite enough. Monitor arms are always a challenge at that scale, though.