So, Brad and I had thought long and hard about when and how to tell Zander that he was going to be a big brother. And in a perfect world, we might have waited until I began to "show" more. However, if by some chance, he found out by accident or overheard someone say "Congratulations," we didn't want him to feel left out, etc.
Last weekend, one morning Brad made omelets and bacon and had Zander bring it up to me in bed. (I heard a little voice say, "Mommy, open the door." And there he was, carefully and proudly holding a full-sized plate with which he had walked up the stairs.) I took the plate downstairs and joined them for breakfast.
At some point, we just realized it was the right time to tell him that he was going to have a baby brother or sister. First he commented that he would be just like two of his friends who already have younger siblings. (In reality, most of his friends already have them, but that's another story.)
Then, he excitedly said, "Can we name the baby we are going to get ZANDER?!" From there we dissolved into giggles imagining saying things like, "Time to brush your teeth Zander," and having both children come running.
Zander said, "Yes, I want that."