Dink, I agree I would stop lying to your kids if it's not mutual.
You don't need to be tell-all. "Whose decision was it and why?!" "That's between your mom and I." I don't believe my kids are served by knowing the reasons I left my XW, but I try to be honest, and don't makeup stories around it either.
I'd take some time to consider what more you want to tell them if anything. You have your whole life to add to what you tell them, but you can never subtract from what you've told them.
