I'd think the best answer would be to keep these toddlers away from the computer, but like I say, with a laptop you can go to device manager and uninstall the keyboard driver. It will get reinstalled next time it boots up.
This is for my sister really. I live far away and like to skype with her and my twin one year old nephews. Problem is, they love to 'play' with the keyboard as well, which often means they accidentally hang up or generally cause havoc. Is there an easy way to disable the keyboard and then later re-enable it? This is for Windows 7.