Suitable childrens games for Linux

[rix]

    I know this is off topic, but I was wondering if anyone could 
suggest a game that my oldest son could play that runs good on Linux? I 
personally wouldn't mind if he played UT2004 (he's 12) but his mom 
wouldn't like it too much. I know that he really likes the Star Trek 
games alot and those do have some violence but the amount in UT2004, 
even with the no gore setting on, would be pushing it. Preferably 
something with good graphics and alot of action.

             TIA. Rick Belins