Lalafell's get a pass mainly because of how similar they are to Tarutaru, since that's what the 1.0 team were going for (and I can't exactly demand SE to delete Lalafell's). Depending on the glamour you go for, they'll only look like children if that's what you're aiming for. Otherwise they just look like really short adults (at least, to me they do). I believe Yoshi-P also said something about the proportions of Lalafell's being a little different to children (heads too big or something), which was a response to people asking for Miqo'te children to be playable (that's a big no from me, too).

With the childlike Viera concept art... they look 100% like children. Very similar to Miqo'te children in design, now that I think about it.

And I'm only suggesting the short burly Viera be the second clan. That way those who want the tall elegant Viera get what they want and those who want something short that isn't cute (for a change) get something as well. It's win-win in my eyes.