Hi Necro
One thing you could try, depending on the quake engine you are using, is the
cl_notifylines 0 command. It effectively shuts off chat messages from appearing on screen. I tend to use it quite a bit on some servers when certain individuals are present and admins are not intervening as it means you can have a game without abuse. You do still get the "beep" but no message so it may be sufficient to censor things for your little one
To reverse it type cl_notifylines 4
I know the Qrack Quake engine had a form of
cl_mute command but I never tried that out.
Hope this is of some use to you
Kind regards
Monty