Since its a Acer netbook your going want to use
unetbootin for windows if your using a windows or linux laptop...
Don't know the model your explaining to use so I figure it has a small screen space...
In this case I would advice using one of the following OS's
1.
Ubuntu Remix ---- Ubuntu/Debian
2.
Jolicloud ---- based on Ubuntu/Debian
3.
Moblin ---- based on intel taking control of intel chipsets.... ops becareful seems to have trouble with Acer Aspire one netbooks
4.
google OS ---- when it becomes available... its a beta write now...
If your nephew wants to do more then just chat online then I would go with Ubuntu Remix, Moblin or Jolicloud. Google Os when it gets hear in the near future will allow you to save documents only online with google apps...
Watch the videos to get idea what you like...
good luck...
later...