How do I connect my Nintendo DS to Nintendo WFC through my Apple Time Capsule?

I have an Apple Time Capsule set up as my wireless router. My brother has a Nintendo DS and loves playing it over Nintendo Wi-Fi Connection. When he tries to connect the DS to the Time Capsule, it says that it’s security doesnt support the DS. Is there any way I can connect them (without plugging in a computer and using Internet Sharing. We’re doing that now and we can’t do it much longer. It’s defeating the purpose of a wireless router)?