It has short doors.

please be elf children please be elf children...
You know that the ONLY races the children will be are Bretons, Imperials, Nords and Redguards, just like in vanilla.

That said, I hope they eventually add in the missing child races as well as the missing race and gender marriage options. It would be weird if you and your spouse were elves or Argonians or Khajiit, yet your children are humans, which I have no problem with per say, but considering that the theme is immersion and roleplaying, it would feel to me that there's something missing, and that they will probably receive a bit of flak, like when the beast races didn't get the glowing eyes in Dawnguard, for example.
I must say, though, that I definitely did not see this DLC coming, that much is for sure. Not that it's a bad thing, at least in my opinion.