Just to be clear - the wireless isn't an alternative to the modem - at least with cable. You plug the wireless router into the cable modem.
Most wireless routers have wired connections that you plug your computer into while your son connects his laptop wirelessly. That's exactly what I've got set up.
In fact, I've posted this message from my desktop PC connected by wire ....
---------- Post added at 18:30 ---------- Previous post was at 18:27 ----------
... and this one from my laptop connected wirelessly
Ain't technology wonderful?