It will work as you describe.
Only restriction is that you'll have to leave the desktop switched on and connected to broadband if you want the laptop to share the same connection over wifi. This assuming you currently have a USB broadband modem. Doesn't apply if your modem has an ethernet interface.
If you want to have wireless/router/hub that also acts as broadband/adsl modem I'd suggest D-Link's
G604T
hth
Charles