Quicksilver G4 needs internet connection

I'm resurrecting my Power Mac G4 (2002) to handle my kid's stuff. I currently have cable internet and D-Link wireless router to handle two other home computers. What is the least expensive yet best way to get the G4 connected to the wireless? I was reading about the AIrport Card but there seems to be compatibility and speed issues. Lastly, I don't know if a third online users will compromise the existing set up? Thanks.