if you have a wired router buy a wifi bridge/access point that plugs into your router this will give wifi access from your wired router
alternatively just buy a normal 802.11G wifi USB adapter that would work
just make sure if your using it for DS then you use WEP encryption and not WPA as it will not work with the DS!
REMEMBER too that the NINTENDO wifi ADAPTER by default will NOT work with the PS3 you would have to soft mod it to make it into a normal wifi adapter to connect the PS3