“When Should We Tell Them?”
I’d say–and most sites agree–as soon as possible. Your goal is well-adjusted kids who have ownership in your decision, and who can eventually follow God courageously in their own life decisions.
If your kids keep secrets as well as mine did didn’t, I know it can be hard to discern (“What if they tell people in Sunday School and our cover is blown? We’re not ready to tell the whole church”). But even before you tell-them-tell-them, you can start planting seeds in your kids’ heads.
Your first year overseas has a way of rearranging your life, your brain, your family, your body. So it makes sense your holidays would follow. 
Missed Part I? Grab it here.
One of the biggest stresses on my engagement wasn’t really the normal stuff–the wedding planning or whatnot. It was a phrase I’d rerun over in my head a hundred times: I don’t feel called overseas. Evangelism is not my gift. My husband-to-be surpassed the one I’d been looking for so many times over. And it really did seem God was leading us to marriage.
I grew up overseas. In fact, I attended 15 different schools by the time I graduated high school. So you could say I’ve experienced my share of goodbyes. (Usually I was the one leaving.)