He's three - he can pick his picture from a list, but asking him to remember his password is pushing it a bit I think...
This isn't as easy as you'd think. For the whole dirty story, see this Launchpad entry.
For the quick how to
Make it possible to log in on a console without a password by starting up a terminal and typing:
sudo passwd -d usernameGoesHere
Change the login screen to use a list of users you can click on by going to System -> Administration -> Login Window and after putting in your password select the Local tab. Under Style, pick one of the options that mention a face browser.
Still won't work yet though :-) Last, add 128 (yes, 128) lines to
It should look like this
and keep going until you hit 63
# Local X displays
Hope this helps...