While integrated access points and routers are only $20 more expensive than the access point itself, it’s the best way. An access point basiaclly expands a wired network to include wireless clients, so you’d have connectivity just as if you were wired to the LAN.
You’ll also need a wireless NIC for each PC on the wireless network. USB models are fine if you don’t want to waste a PCI card slot, and for laptops my favorite are the 3com XJack ones where you don’t need to remove the card to throw the laptop in the laptop bag. Generally laptop models are the cheapest, followed by USB models (which btw perform much like PCI ones) and then PCI models with an antenna sticking out the back of your PC.