This is really only for
L4D support, but since you asked so nicely...
If your family already has an internet connection, you can just hook up to that, either with a wired to a router, or wirelessly to a wireless compatible router or access points.
How does your family connect to the internet now?
If they have a wireless compatible router (like a Linksys WRT54G or something similar), then all you need is a wireless card to connect.
Generally, for gaming, you really want a wired connection, but if wireless is your only option, then you will just have to go with it.