Don't mess with the waterbender

Tenzin: "Haha, Bumi wet his pants! Bumi wet his pants!"
Bumi: "NO I DIDN'T!"
Tenzin: "...Bumi wet his pants!"
Bumi: "No, IT WAS KYA!"
Tenzin: "BUMI WET HIS PANTS!"
Bumi: -.-
Kya: "You deserved it."

So, these crazy kids are Aang and Katara's children: Kya (the waterbender girl), Bumi (the poor non-bender boy on the right) and Tenzin (the little airbender boy).
There are still no official images showing how they looked like as children, so this is pure speculation from my side. (There are however a few images showing how they look like when they are older.)
I'm pretty sure I'll draw them again when I have more references for Kya & Bumi.

Edit 14 july 2012: I think I'm gonna make a new version of this picture now that we know a bit more about these characters. I won't delete this picture either way, I'll just add a link to the new one when it's done.

Tenzin, Kya & Bumi - Avatar the last Airbender / The Legend of Korra (c) Nickelodeon, Mike & Bryan
Art (c) BlueDecember89