Don't make assumptions about what your kids understand. Speak to them often, plainly, without a tone of judgement or an air of presupposition. Important times are ahead and you are not going to want to screw them up. What you're going to need to do is practice talking to your children in a mature fashion, using a calm and relaxed disposition, so that it is second nature to you. Because there are some conversations you just won't see coming.
My nephew has a black Daddy that he hasn't seen in over a decade and a white Mama, my sister, that he has known his whole life. He is a young teenager now, but when he was five years old he taught me a lesson at the Sam's Club food court I will never forget. The rest of the family (read: the women) were off doing the hard work of shopping. So it was just he and I sitting there, hanging out. I didn't have children at the time and I remember something peaceful came over me. Here I was sitting with a five year old kid doing absolutely nothing, and it felt very, I don't know, right I guess. I should have been in one of my world famous, shopping-induced, foul moods, but I wasn't. This is how it should be, I thought. Man and boy, eating hot dogs, bonding together in spite of age and a complete lack of words.
But then an unexpected heaviness invited itself to our crummy, fiberglass table and sat down beside us in one of our crummy, fiberglass seats. I realized in a split moment that I was not the man who was supposed to be doing this. This boy had a father and I knew that my nephew would never be able to have his dad in the way a boy needs. I was Uncle Chris. I wasn't Dad and I never would be. My heart became lethargic as my peaceful mood was buried beneath this data, this... tangle of information.
So I looked at him and I said, "You know what? I'm lucky I get to be your Uncle."
I continued, "It's true, you're pretty terrific. Did you know that?"
Then his face softened and he got, well, almost contemplative. "Really?" he asked as he made eye contact with me.
"Well DUH," I responded incredulously, and then I added, "When your Aunt and I have kids one day, I hope I have a son. And I hope he turns out to be just like you."
He studied me as I finished. He looked straight into my eyes and positively studied my face, even after I stopped talking. The silence was almost awkward, just short of unnerving, and finally he spoke.
"You want him to be just like me?" he searched. "Even my same color?"
And there it was. The moment. The kind of moment that, as a parent, you both long for and fear at the same time. But as an Uncle, you get utterly blindsided by its very existence. One second I'm sucking down a hot dog twice as long as my large intestine, the next I'm staring down a once in a lifetime opportunity to validate this boy's very existence. This five year old embodiment of self worth was looking up at me and asking a question as old as history itself, "Am I acceptable?"
I met his gaze without hesitation and I lowered my face to be even with his. In a soft, confident tone I said to him, "Christian, I wouldn't change a single thing about you. If your Aunt and I had a baby that looked exactly like you, I'd be the happiest Daddy on the planet." I stopped there and let it sink in. I went back to my hot dog.
After a few moments had passed I added casually, while licking my lips and chewing my food, "You realize that won't happen, though, right? Since I'm a cream colored guy and your Aunt is a cream colored girl, we can't make little brown babies. We're stuck with little creamy ones."
He looked dubious.
"Let's take you for example. Your skin is brown because your Mommy is cream colored like me. But your Daddy, the one that lives far away, is a darker brown color like that man over there, see him? That's why your skin is light brown. You got some color from your Mommy and some color from your Daddy."
He sat there, expressionless, for a full two seconds. Then he shot up unexpectedly, and raised one arm over his head before bringing it down swiftly, pounding his fist into the palm of his open hand while exclaiming loudly, through a triumphant, goofy-looking grin, "I KNEW IT!" I almost choked on my food from laughing. He thought this was some kind of deep, dark family secret or something, and he had finally cracked the case!
So I say again, do not make assumptions about what your kids understand. Talk to them early, and plainly, and often. And get really good at mastering that relaxed, calm, and confident disposition. You never know when a teaching moment will present itself.
But most of all, validate the young ones in your life. Answer the visible questions, but also seek out and answer the ones that lie beneath the surface. Because if you don't, I promise that someone else will. And they will not necessarily have your kids best interests at heart.