A Virtual LAN for WEP

My router does not support WEP which is understandable considering using WEP is tantamount to no security at all. I presently have an unmanaged switch connected to the router so I have more wired ports.

Unfortunately, my Nintendo handheld supports only WEP (and no encryption). Nintendo closed their Wifi Connect service some time ago, so the device no longer needs any Internet access. But it does need to connect with a Pentium 3 box I have reserved for my game saves, DS Linux files, and other Nintendo-related things. This box will join my KVM, but I don't want it to have access to the Internet or my existing LAN. I can easily backup the P3 with a Clonezilla CD and USB hard drive. In the unlikely event I need the P3 to exchange files with my i7 boxen, I can always use sneakernet (a USB flash drive).

I already have a spare 802.11g access point that does support WEP. My thinking is I can upgrade to a managed switch with VLAN support to isolate the DS, the P3 box, and the WAP. Perhaps nobody will ever see and bother with my WEP WLAN, but I will go on the assumption it will be hacked on day one. And once that happens, I assume the VLAN will keep Mr(s) Hacker from getting beyond the P3 box.

Before I invest in a managed switch, is this approach able to meet my needs?