What a jerk
I will freely admit I don't really like kids and I don't really like sitting near them on the plane. However, that said, I don't get to choose. I sit where I'm assigned and roll with it. Sometimes the kids are great sometimes they're not. Ive sat next to cute and funny kids and one time i had OJ spilled all over my suit on the way to work. But hey, it's the same with adults!
Your wife was immensely polite. I'm not sure I would have moved.