The way I do it is to have a wireless adsl router which is connected to the adsl (broadband) connection on the phone. Then each computer has a small usb wireless network adaptor plugged in. Netgear has proved to be very reliable. If the laptop has a Centrino processor it may have a built in wireless connector.
For the ADSL router you should allow around £80, and the usb adaptors will be around £30 each (although you could shop around).