I have made it a principle that I will never lie to my kids. I had so many trust issues with my own parents (which I do not want to make public in any fashion) that this is, to me, an iron law. My children already know that they can ask me any question and I will answer as honestly as I can. That every decision I make has a logical reasoning behind it that I will explain to them in full. And when they inevitably ask me awkward questions or make requests whose answers or reasons are not appropriate for their age, I will tell them that I have a reason and that they should just trust me.

Now, that last bit is common to most parents - but if I work hard enough on the first half, instances of the latter will be infrequent enough (and my children will be so used to the idea that their daddy has a good reason for everything) that they actually will trust me.