Hardware :: Set Up A Guest Network With 1st Gen TC + Router?

My current setup is a first gen TC running at 802.11n 5GHz with a Linksys WRT54GS in bridge mode broadcasting 802.11b/g. Both are WPA2 networks, and the setup has been great so far.

When the new AEBS/TC came out, I was looking at the guest network capability and that's got me wondering if there's any way I can create such a network with my setup. I would love to have a network for my DS and PSP to be able to join and would preferably like to have it unsecured to avoid connection issues.

I'm well aware that my TC doesn't have the proper hardware to do that by itself, but is there any way I can create a guest network to allow access to the Internet but not any networked computers on the main network? Would I need a seperate router to do this, or would my current setup be sufficient? What settings would I need, or can this even be done?

Come to think of it, would it just be easier for me to setup an additional gateway using a third router, hide the SSID and have it unsecured? (Although I'd be afraid of compromising my network's security with this method.)