I feel the same way as you do. This is how my parents did it and I'm doing the same with my kids.
The goal is to tell your child, when they find out Santa is not real, that it wasn't something you told them but something they came up with it on their own and from their friends and society. You didn't lie to them, but society (friends and media) led them to believe in Santa and you let them do it. The reason you let them do it is because there was no harm in it. You could make it a teaching moment but that's for another post.
Regarding questions, be as vague as possible. Avoid statements like 'Santa is coming' or 'Santa's watching and is going to be upset'. Instead, turn them into questions like 'Is Santa coming?' or 'I hope that doesn't get you a piece of coal in your stocking'.. In fact, being vague and the unknown makes their imagination even more vibrant and makes it more intriguing.
Remember we're not dealing with deep morality here so if you don't weigh in, it's not immoral. As you say, the older kids have taken over, as have mine. I've told my older kids what the end goal is, and they have more fun with it than I did.
This way, when they find out, you can tell them 'I never told you there was a Santa. This is something you came up with on your own. Hope this helps.