There is no definitive answer, but from my experience:

I'm Swedish but my mother is Finnish. My mother taught me a little Finnish when I was a kid; in fact, she spoke mostly Finnish with me. When I started school and all the other kids were speaking Swedish I wanted to speak Swedish with my mother too, so I pretended I didn't understand Finnish whenever she tried. I just shouted "Prata svenska!" (speak Swedish.) So she stopped speaking Finnish with me.

And that is one of my biggest regrets in my life.

Things are so easy to learn when you're small, and I could have been trilingual by now. I could have spoken the same language half of my relatives speak. I really wish I knew Finnish, but I don't. And it will take hell of a long time to learn it now, given that I have time for such a thing when I'm done studying.

I don't really have any kind of point here, just want to give you the kids possible feelings about such a thing.

When thinking about layouts, you have to look at it from an international perspective,  Qwerty may be popular but it isn't the only layout.

Sounds like you like the idea of an international layout,  but I'm not sure if such a layout exists.  The number pad is probably the closest you'd get.

Before 18, kids are greatly influenced by peers and standards imposed by society. Therefore, I think that parents should let kids learn Qwerty touch typing to get some proper train first. That will impress their friends and help them build their self-confidence, that they can do things.

After they reach puberty and about to be a grown up adults, then you may show them other alternative layouts and let them choose to stay with Qwerty or start their switch to another layout.

The decision should be theirs, not ours.