Since I've come here myself for help I am far from an expert in the field, but I'll give you my 2 cents.
I always think of a wireless router like a radio station transmitter. A signal is sent out. If I came to your house with my laptop that is capable of receiving this signal then I could connect along with you. But in your case the other 2 computers don't have the means to receive this signal.
You could plug in to a USB port, on the other computers, a Wireless G USB Adapter. Kinda looks like an antenna if you set it up in a stand they sometime give you. NOW, suddenly, your other computers have a way of capturing the signal that the wireless router is sending out.
If any of the other computers have an Ethernet plug in it, I would guess you could hard wire it directly to the router itself.
Here is a link to such an item as I've mentioned that I used myself. But I don't know of anyway to share your signal directly from the laptop.
http://catalog.belkin.com/IWCatProductPage.process?Product_Id=179211
Jim